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Wang, Wen, Xiao-Gang Wang y Xuan Zhou. "Impacts of Californian dams on flow regime and maximum/minimum flow probability distribution". Hydrology Research 42, n.º 4 (1 de agosto de 2011): 275–89. http://dx.doi.org/10.2166/nh.2011.137.
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Dams have major impacts on river hydrology with a general tendency to decrease annual maximum flows and increase annual minimum flows. The analysis of 41 streamflow series in California, USA are examined, and the results show that, as expected, the mean values and variations of annual peak flows and maximum flows of different durations are reduced for almost all sites after dam use, and the larger the ratio of total reservoir capacity to pre-dam annual runoff, the larger the rate of peak flow reduction. However, the impacts on minimum flow are mixed. For five out of seven cases with long data records for periods before and after dam use, the average annual minimum flow as well as its variation increased, but for the other two cases, they decreased. No significant changes are detected for various extreme precipitation indices; therefore, dam construction is believed to be the major reason for flow regime changes. The probability distribution of extreme flows also changed, due to the impacts of dams. The Log-Pearson Type III (LP3) distribution is best for peak flow series and one-day maximum series at sites with or without the impact of dams; the three-parameter Weibull (W3) distribution is the best model for the seven-day minimum flow at sites with no or minor dam impacts, whereas at sites with major dam impacts, the best model is the generalized extreme value (GEV) model for the seven-day minimum flow.
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Nuriyev, A. A. "ŞİRVAN ÇAYLARININ AXIMININ ÇOXİLLİK TƏRƏDDÜDLƏRİ". “Water Problems: science and technologies” 1, n.º 1 (10 de junio de 2021): 38–45. http://dx.doi.org/10.30546/wtst.2020.1.38.
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Abstract. The article is devoted to the analysis of long-term fluctuations of the annual flow of the Shirvan rivers. The analysis used data from 4 rivers with an observation period of more than 50 years. linear trends were identified in the observation series, and their significance was assessed. The annual water discharge observations are divided into two series, covering 1961-1990 and 1991-2018. The dynamics of annual precipitation data of meteorological observation stations located in the study area were also analyzed. Annual precipitation increased in Goychay and Ismayilli meteorological stations, and partial decrease in Gabala and Oguz meteorological stations. The seasonal variation of the annual flow is also analyzed. According to data of Alijanchay and Girdimanchay, a decrease in annual flow was observed, and an increase was observed in Goychay and Turyanchay rivers. The seasonal fluctuations of the flow increased in the cold seasons and decreased in the warm seasons. Keywords: annual flow, long-term fluctuations, linear trends, climate changes
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Burgan, Halil Ibrahim y Hafzullah Aksoy. "Annual flow duration curve model for ungauged basins". Hydrology Research 49, n.º 5 (12 de febrero de 2018): 1684–95. http://dx.doi.org/10.2166/nh.2018.109.
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AbstractA flow duration curve (FDC) plots the percentage of time that flow in a stream is equal to or exceeding a given value. In a gauged basin, it is obtained by sorting the observed flow from the largest to the smallest, and plotting against the corresponding exceedance probability. At ungauged basins where no data exist, the need for developing empirical methods emerges. This study aims at developing an FDC model for ungauged basins. The model is based on the normalized nondimensional annual mean flow quantiles. The annual mean flow is empirically calculated by a regression equation that takes drainage area and annual precipitation as input. Slope of the channel is additionally considered in the regression, however no better performance is achieved. Seyhan and Ceyhan basins in the Mediterranean region in southern Turkey are chosen as the study area. Data from 109 gauging stations are used for the calibration and validation of the model. Gauging stations on the tributaries are studied with a view to limiting anthropogenic activities on the rivers. Results of the application are found so promising that the model can be considered a good foundation for the development of FDCs at ungauged basins.
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Horn, Dennis R. "Annual Flow Statistics for Ungaged Streams in Idaho". Journal of Irrigation and Drainage Engineering 114, n.º 3 (agosto de 1988): 463–75. http://dx.doi.org/10.1061/(asce)0733-9437(1988)114:3(463).
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Tiwari, Harinarayan, Subash Pd Rai, Nayan Sharma y Dheeraj Kumar. "Computational approaches for annual maximum river flow series". Ain Shams Engineering Journal 8, n.º 1 (marzo de 2017): 51–58. http://dx.doi.org/10.1016/j.asej.2015.07.016.
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Gudmundsson, Gudmundur. "Disaggregation of annual flow data with multiplicative trends". Journal of Forecasting 18, n.º 1 (enero de 1999): 33–37. http://dx.doi.org/10.1002/(sici)1099-131x(199901)18:1<33::aid-for687>3.0.co;2-t.
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Suwal, Naresh, Alban Kuriqi, Xianfeng Huang, João Delgado, Dariusz Młyński y Andrzej Walega. "Environmental Flows Assessment in Nepal: The Case of Kaligandaki River". Sustainability 12, n.º 21 (22 de octubre de 2020): 8766. http://dx.doi.org/10.3390/su12218766.
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Environmental flow assessments (e-flows) are relatively new practices, especially in developing countries such as Nepal. This study presents a comprehensive analysis of the influence of hydrologically based e-flow methods in the natural flow regime. The study used different hydrological-based methods, namely, the Global Environmental Flow Calculator, the Tennant method, the flow duration curve method, the dynamic method, the mean annual flow method, and the annual distribution method to allocate e-flows in the Kaligandaki River. The most common practice for setting e-flows consists of allocating a specific percentage of mean annual flow or portion of flow derived from specific percentiles of the flow duration curve. However, e-flow releases should mimic the river’s intra-annual variability to meet the specific ecological function at different river trophic levels and in different periods over a year covering biotas life stages. The suitability of the methods was analyzed using the Indicators of Hydrological Alterations and e-flows components. The annual distribution method and the 30%Q-D (30% of daily discharge) methods showed a low alteration at the five global indexes for each group of Indicators of Hydrological Alterations and e-flows components, which allowed us to conclude that these methods are superior to the other methods. Hence, the study results concluded that 30%Q-D and annual distribution methods are more suitable for the e-flows implementation to meet the riverine ecosystem’s annual dynamic demand to maintain the river’s health. This case study can be used as a guideline to allocate e-flows in the Kaligandaki River, particularly for small hydropower plants.
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Georgiadi, Alexander G., Irina P. Milyukova, Oleg O. Borodin y Artyom V. Gusarov. "Water Flow Changes In The Don River (European Russia) During 1891–2019". GEOGRAPHY, ENVIRONMENT, SUSTAINABILITY 16, n.º 2 (27 de junio de 2023): 6–17. http://dx.doi.org/10.24057/2071-9388-2022-083.
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The Don River Long near Razdorskaya Village had long phases (lasting 33–86 years) of increased/decreased naturalized annual and seasonal water flow, and their properties for 1891–2019 were identified. Long-term changes in the annual and snow-melt flood flow occurred in the opposite phase relative to changes in the winter and summer-autumn flow. Annual hydrographs in the phase of decreased flow were characterized by an increase in water discharge during the low-water seasons of the year, but a noticeable decrease in daily flood water discharge and maximum water discharge. The share of high-water years (years with a flow exceedance probability equal to or less than 25%) in the phase of increased flow is significantly higher than the share of low-water years (years with a flow exceedance probability equal to or more than 75%). And on the contrary. At the same time the cumulative share of low- and high-water years remains relatively stable. The total changes in the annual and seasonal flow, caused by both anthropogenic and climatic factors, throughout the entire period of modern global warming (since 1989) consisted in a decrease of the annual and snow-melt flood flow and an increase of flow values during low-water seasons.
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Zhukov, Igor, Nickolay Pechurin, Lyudmila Kondratova y Sergey Pechurin. "GDP in Value as a Measure for Evaluating Annual Data Flow Increase on IoT". Advances in Cyber-Physical Systems 4, n.º 2 (23 de septiembre de 2019): 137–42. http://dx.doi.org/10.23939/acps2019.02.137.
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Pastor, A. V., F. Ludwig, H. Biemans, H. Hoff y P. Kabat. "Accounting for environmental flow requirements in global water assessments". Hydrology and Earth System Sciences Discussions 10, n.º 12 (10 de diciembre de 2013): 14987–5032. http://dx.doi.org/10.5194/hessd-10-14987-2013.
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Abstract. With growing water needs for food production, it is necessary to improve the quantification of "Environmental Flow Requirements (EFRs)" to secure enough water for the freshwater ecosystems. In this study, five methods for calculating EFRs were compared to 11 case studies of locally-calculated EFRs. Three of the methods already existed (Smakhtin, Tennant and Tessmann) and two were developed in this study (the Variable Monthly Flow method and the Q90_Q50 method). The Variable Monthly Flow (VFM) method mimics for the first time the natural flow regimes while being "validated" at global and local scales. The VFM uses algorithms to classify flow regime into high, intermediate and low-flow months to take into account intra-annual variability by allocating EFRs with a percentage of mean monthly flow (MMF). The Q90_Q50 method allocates annual flow quantiles (Q50 and Q90) depending on the flow season. The results showed that, over all methods, 37% of annual discharge was allocated to "Nature" with a higher pressure on low flow requirements (LFR = 46% to 71% of average low flows) than on high flow requirements (HFR = 17% to 45% of average high flows). Environmental flow methods using fixed annual thresholds such as Tennant, Q90_Q50 and Smakhtin seemed to overestimate EFRs of stable flow regimes and underestimate EFRs of variable flow regimes. VFM and Tessmann methods showed the highest correlation with the locally-calculated EFRs (R2 = 0.91). The main difference between the Tessmann and VFM methods is that Tessmann method does not allow any water withdrawals during the low-flow season. Those five methods were tested within the global vegetation and hydrological model LPJml. The calculated global annual EFRs for "fair" ecological conditions represent between 25 to 46% of mean annual flow (MAF). Variable flow regimes such as the Nile have lower EFRs (ranging from 12 to 48% of MAF) than stable tropical regimes such as the Amazon (EFRs ranging from 30 to 67% of MAF).
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Rostami, Sajjad, Jianxun He y Quazi K. Hassan. "Water quality response to river flow regime at three major rivers in Alberta". Water Quality Research Journal 55, n.º 1 (26 de septiembre de 2019): 79–92. http://dx.doi.org/10.2166/wqrj.2019.033.
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Abstract Both anthropogenic activities and natural factors affect river water in quantity and quality, while anthropogenic activities have been often blamed to cause water quality temporal degradation. In addition, riverine water quality displays intra-annual/seasonal variations, which are often more prominent than inter-annual variations. The intra-annual variations in water quality, which are attracting the attention of managers and policy-makers, beg the question of how to better manage riverine water quality at a finer time resolution. The natural factors, in particular, the hydro-meteorological variables, could be the primary drivers of the intra-annual variations of riverine water quality. Therefore, this paper examined the association between riverine water quality and one hydro-meteorological variable (flow) with the focus on their relationship at the intra-annual timescale on three selected rivers in Alberta, Canada. The results demonstrated that flow drives intra-annual variation of riverine water quality in general. Moreover, some water quality parameters responded to flow distinctively at three flow regimes (low, medium, and high flows). Water quality parameters were categorized into eight groups according to their responses to flow at the flow regimes. These implied the challenges in water quality management while providing insight into how to formulate more effective water management strategies.
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Arefiev, N. V., N. S. Bakanovichus, A. A. Lyalina, N. V. Sudakova, T. S. Ivanov, S. P. Kotlyar y M. V. Petroshenko. "Development of an Automated Approach for Updating of the Annual Runoff Module Map". Environment. Technology. Resources. Proceedings of the International Scientific and Practical Conference 2 (17 de junio de 2015): 35. http://dx.doi.org/10.17770/etr2015vol2.259.
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<p>Several Russian Hydropower Design and Research Institutes have recently fulfilled studies of hydropower potential estimation for NorthWest, Caucasian and Angara River’s regions in Russia. An approach to automate the calculation of river flow characteristics, based on the usage of annual flow rate map, was proposed and tested by the authors for the aims of the studies.</p><p>Annual river flow characteristics together with the terrain data are the most important data sources for evaluation of the hydropower potential.</p><p>A set of requirements was made for the approach and for automation of annual flow rate maps creation in order to provide ability for updates in every 5-10 years.</p><p>A problem of lack of hydrological data for small and medium sized rivers was faced. To determine the hydrological characteristics the Russian code specification "Determination of Design Hydrological Performance" was used for the conditions of the lack of hydrological data, methods of spatial interpolation were also used.</p><p>To solve the problems it is necessary to define the parameters of the annual flow distribution: average annual flow, variation coefficient, coefficient of skewness.</p><p>Mapping is based on the assumption of a smooth change of annual flow rate for any territory in accordance with the distribution of climatic and physiographic factors (topography, soil, groundwater depth, etc.).</p><p>Milestones of flow rate mapping included: preparation of hydrological initial data; creating of the updated flow rate maps; determination of the corrections to the influence of local azonal factors; estimation of the accuracy of flow characteristics calculations.</p><p>In order to update the annual flow rate maps a special GIS application “Hydrologist” was created. The GIS application includes computer-assisted tool for processing the hydrological data, import/export tools, tools for analysis of area zoning data, tools for analysis of annual flow rate values in centroids of drainage-basins, location of water stage gauges, also the old and updated flow rate maps.</p><p>The article deals with the approach description, main problems that were faced and presenting the results.</p><p>The technology has been applied for North-West, Volga and Siberian Federal Districts in Russia. Comparison of the created annual flow rate map with the previously used map shows that the updated map is better of acquiring hydrological data for small and medium sized rivers.</p>
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Hughes, JMR y B. James. "A hydrological regionalization of streams in Victoria, Australia, with implications for stream Ecology". Marine and Freshwater Research 40, n.º 3 (1989): 303. http://dx.doi.org/10.1071/mf9890303.
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Annual, monthly, low and peak flow data were used to classify and ordinate 138 stream gauges in Victoria. Sixteen hydrological variables were used and low-flow and entire-flow regionalizations were derived. The low-flow regionalization was spatially indistinct and therefore unusable, but the entire-flow regionalization produced five distinctive and spatially significant regions. Least-squares relationships were calculated between mean annual runoff, catchment area and coefficient of variation of annual flows, and the 16 variables. Rivers in the dry western districts of Victoria exhibit high variability of annual, monthly and peak flows, and low specific low flows. The converse is true for rivers in the western highlands of Victoria. Stream regionalizations are a useful tool for stream ecologists, and may be used for generating hypotheses, for detecting representative rivers and for producing baseline stream surveys.
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Chen, Rongchang, Chen Liu, Xiaofeng Luo y Wei Shen. "Numerical Simulation Study of Booming Effect in Fast Currents of Inland River". E3S Web of Conferences 38 (2018): 03048. http://dx.doi.org/10.1051/e3sconf/20183803048.
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In the downstream tidal section of the Yangtze River, nine kinds of combinations of hydrological environmental conditions are considered, including the annual average runoff flow, the annual average peak flow and the flood control design flow, as well as the three conditions of spring, medium and neap tides. By means of the numerical simulation method, the effective performance parameter values for conventional intercepting boom under different environmental conditions are obtained by simulating 9 kinds of maximum current speed to withstand, Max.CS, respectively. The results show that, in the downstream fast current tidal section of the Yangtze River, for the boom performance index of Max.CS, the relatively extensive applicability value should be 3.0kn under the condition of the annual average runoff flow; 4.0Kn should be selected under the condition of the annual average peak flow; and 4.5Kn should be selected under the flood control design flow. This study can provide technical support for the design, selection and use of booms in downstream waters of the Yangtze River.
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Courtillot, Vincent, Jean-Louis Le Mouël, Fernando Lopes y Dominique Gibert. "On the Nature and Origin of Atmospheric Annual and Semi-Annual Oscillations". Atmosphere 13, n.º 11 (15 de noviembre de 2022): 1907. http://dx.doi.org/10.3390/atmos13111907.
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This paper proposes a joint analysis of variations of global sea-level pressure (SLP) and of Earth’s rotation (RP), expressed as the coordinates of the rotation pole (m1, m2) and length of day (lod). We retain iterative singular spectrum analysis (iSSA) as the main tool to extract the trend, periods, and quasi periods in the data time series. SLP components are a weak trend, seven quasi-periodic or periodic components (∼130, 90, 50, 22, 15, 4, 1.8 years), an annual cycle, and its first three harmonics. These periods are characteristic of the space-time evolution of the Earth’s rotation axis and are present in many characteristic features of solar and terrestrial physics. The amplitudes of the annual SLP component and its three first harmonics decrease from 93 hPa for the annual to 21 hPa for the third harmonic. In contrast, the components with pseudo-periods longer than a year range between 0.2 and 0.5 hPa. We focus mainly on the annual and, to a lesser extent, the semi-annual components. The annual RP and SLP components have a phase lag of 152 days (half the Euler period). Maps of the first three components of SLP (that together comprise 85% of the data variance) reveal interesting symmetries. The trend is very stable and forms a triskeles structure that can be modeled as Taylor–Couette flow of mode 3. The annual component is characterized by a large negative anomaly extending over Eurasia in the NH summer (and the opposite in the NH winter) and three large positive anomalies over Australia and the southern tips of South America and South Africa in the SH spring (and the opposite in the SH autumn), forming a triskeles. The semi-annual component is characterized by three positive anomalies (an irregular triskeles) in the NH spring and autumn (and the opposite in the NH summer and winter), and in the SH spring and autumn by a strong stable pattern consisting of three large negative anomalies forming a clear triskeles within the 40–60∘ annulus formed by the southern oceans. A large positive anomaly centered over Antarctica, with its maximum displaced toward Australia, and a smaller one centered over Southern Africa, complement the pattern. Analysis of iSSA components of global sea level pressure shows a rather simple spatial distribution with the principal forcing factor being changes in parameters of the Earth’s rotation pole and velocity. The flow can probably best be modeled as a set of coaxial cylinders arranged in groups of three (triskeles) or four and controlled by Earth topography and continent/ocean boundaries. Flow patterns suggested by maps of the three main iSSA components of SLP (trend, annual, and semi-annual) are suggestive of Taylor–Couette flow. The envelopes of the annual components of SLP and RP are offset by four decades, and there are indications that causality is present in that changes in Earth rotation axis lead force pressure variations.
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Liu, Shuiqing, Zuhao Zhou, Jiajia Liu, Jia Li, Pengxiang Wang, Cuimei Li, Xinmin Xie, Yangwen Jia y Hao Wang. "Analysis of the Runoff Component Variation Mechanisms in the Cold Region of Northeastern China under Climate Change". Water 14, n.º 19 (8 de octubre de 2022): 3170. http://dx.doi.org/10.3390/w14193170.
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Climate change alters hydrological processes in cold regions. However, the mechanisms of runoff component variation remain obscure. We implemented a WEP-N model to estimate monthly runoff in the Songhua River Basin (SRB) between 1956 and 2018. All flow simulations were accurate (NSE > 0.75 and RE < 5%). The annual runoff was attenuated in 1998, and the hydrological series (1956–2018) was divided into base and change periods in that year. Relative to the BS (base scenario), annual production flow reduction was −28.2% under climate change and water use. A multifactor attribution analysis showed that climate change and water use contributed 77.0% and 23.0% to annual runoff reduction, respectively. Decreases in annual surface and base flow explained 62.1% and 35.7% of annual production flow reduction, respectively. The base flow increased by 8.5% and 6.5% during the freezing and thawing periods, respectively. Relative to the BS, groundwater recharge increased by 9.2% and 4.1% during the freezing and thawing periods, respectively, under climate change conditions. Climate change was the dominant factor attenuating production flow. The change in production flow occurred mainly during the non-freeze-thaw period. The decrease in total production flow in the SRB was caused mainly by the decrease in the surface flow, where the reduction in base flow accounted for a relatively small proportion. Production flow attenuation aggravated water shortages. The utilization rate of groundwater resources is far below the internationally recognized alarm line. Therefore, attention should be directed towards certain areas of the SRB and other regions with minimal groundwater exploitation.
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Hulley, Mike, Colin Clarke y Ed Watt. "Low flow frequency analysis for stream with mixed populations". Canadian Journal of Civil Engineering 42, n.º 8 (agosto de 2015): 503–9. http://dx.doi.org/10.1139/cjce-2014-0323.
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A methodology is developed for the estimation of annual low-flow quantiles for streams with annual low flows occurring in both the summer and winter. Since the low flow generating processes are different in summer and winter, independent seasonal analyses are required. The methodology provides recommendations for assessment of record length, randomness, homogeneity, independence and stationarity, as well as guidelines for distribution selection and fitting for seasonal distributions. The seasonal distributions are then used to develop the combined distribution for annual low flow estimation. Four worked examples of long-term Canadian hydrometric stations are provided.
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Adlul Islam, Alok K Sikka, B Saha y Anamika. "Modelling Sensitivity of Stream flow to Climate Change in the Brahmani River Basin". Journal of Agricultural Engineering (India) 46, n.º 4 (31 de diciembre de 2009): 49–53. http://dx.doi.org/10.52151/jae2009464.1393.
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It is widely accepted that increasing concentration of greenhouse gases in the atmosphere is causing climate change, which may alter the hydrologic cycle and regional water availability. Hydrological modelling to assess the sensitivity of stream flow in the Brahmani basin to different hypothetical climate change scenarios indicated significant changes in mean monthly stream flow. Simulation results indicated 76% increase in annual stream flow with a 30% increase in rainfall and no change in temperature, and a maximum decrease of 33% in annual stream flow with 4°C increase in temperature and 10% decrease in rainfall. Rainfall changes had a greater effect on seasonal as well as annual changes in stream flow than the changes in temperature.
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Arfan, M., A. H. Makhdum y G. Nabi. "ASSESSMENT OF TEMPORAL FLOW VARIABILITY OF THE KABUL RIVER". Journal of Mountain Area Research 2 (7 de agosto de 2017): 1. http://dx.doi.org/10.53874/jmar.v2i0.21.
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Water resources estimation under changing flow regimes is required for planning and smooth distribution of water to provinces. Since the hydrological parameters are changing significantly due to climate change, the changes in the pattern of flow regimes are definite. The objective of present study was to assess the spatial and temporal hydro variability of Indus basin. The data of Kabul river at Nowshera before its confluence with Indus river were collected from Surface water Hydrology Project (SWHP), WAPDA. The seasons were divided as three and six month keeping in view the hydrological cycle. Trends and variation were investigated by applying the Mann-Kendall test and Sen’s method. The presence of trends tested at different significant level, 99.9%, 95% and 90%. The overall analysis indicates that there is more flow variation on seasonal basis as compared to the annual basis. The Kabul river showed decreasing trend in the maximum mean annual discharge, whereas the minimum mean annual discharge showed increasing trend. It was concluded that Kabul river showed decreasing trend in annual mean and maximum discharge, whereas annual minimum discharge showed increasing trend. It was also noticed that Kabul river mean minimum discharge time series decreased during 1961-1985, whereas it increased during 1986-2010. It was also found that annual mean and maximum discharge decreasing rate was greater during 1986-2010. It was further concluded that each decade experienced one or two years of both dry and wet periods and that 2000-2004 was the driest period in the history of Kabul River.
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Xu, Zhicheng, Lei Cheng, Peng Luo, Pan Liu, Lu Zhang, Fapeng Li, Liu Liu y Jie Wang. "A Climatic Perspective on the Impacts of Global Warming on Water Cycle of Cold Mountainous Catchments in the Tibetan Plateau: A Case Study in Yarlung Zangbo River Basin". Water 12, n.º 9 (20 de agosto de 2020): 2338. http://dx.doi.org/10.3390/w12092338.
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Global warming has a profound influence on global and regional water cycles, especially in the cold mountainous area. However, detecting and quantifying such changes are still difficult because noise and variability in observed streamflow are relatively larger than the long-term trends. In this study, the impacts of global warming on the catchment water cycles in the Yarlung Zangbo River Basin (YZRB), one of most important catchments in south of the Tibetan Plateau, are quantified using a climatic approach based on the relationship between basin-scale groundwater storage and low flow at the annual time scale. By using a quantile regression method and flow recession analysis, changes in low flow regimes and basin-scale groundwater storage at the Nuxia hydrological station are quantified at the annual time scale during 1961–2000. Results show annual low flows (10th and 25th annual flows) of the YZRB have decreased significantly, while long-term annual precipitation, total streamflow, and high flows are statistically unchanged. Annual lowest seven-day flow shows a significantly downward trend (2.2 m3/s/a, p < 0.05) and its timing has advanced about 12 days (2.8 day/10a, p < 0.1) during the study period. Estimated annual basin-scale groundwater storage also shows a significant decreasing trend at a rate of 0.079 mm/a (p < 0.05) over the study period. Further analysis suggests that evaporation increase, decreased snow-fraction, and increased annual precipitation intensity induced by the rising temperature possibly are the drivers causing a significant decline in catchment low flow regimes and groundwater storage in the study area. This highlights that an increase in temperature has likely already caused significant changes in regional flow regimes in the high and cold mountainous regions, which has alarming consequences in regional ecological protection and sustainable water resources management.
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Imanov, Farda, Irada Aliyeva, Saleh Nagiyev y Harald Leummens. "Changes in the annual flow of the Kura River". Czasopismo Geograficzne 94, n.º 1 (26 de mayo de 2023): 39–52. http://dx.doi.org/10.12657/czageo-94-02.
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The article presents the analysis of changes in the annual flow of the Kura River and its large transboundary tributaries, resulting from climate change and anthropogenic factors, mainly irrigated agriculture. It is shown that a significant change in the flow regime of the Kura River began after the construction of the multi-purpose Mingachevir reservoir in 1953. Morevoer, climate change observed in the river basin since the mid 1990s manifests itself by an increase in air temperature and a decrease in precipitation, which has led to a further decrease in the river’s flow. During the lengthy drought period that began in 2011 and is still in progress, the decrease in the river flow in the downstream section of the Kura River has reached critical levels, causing serious problems regarding not only the irrigation of drylands, but also the supply of drinking water to settlements. The second part of the article describes also other social and economic, as well as environmental consequences of a decrease in the flow of the Kura River.
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Chen, Xiaohong, Lijuan Zhang, C. Y. Xu, Jiaming Zhang y Changqing Ye. "Hydrological Design of Nonstationary Flood Extremes and Durations in Wujiang River, South China: Changing Properties, Causes, and Impacts". Mathematical Problems in Engineering 2013 (2013): 1–10. http://dx.doi.org/10.1155/2013/527461.
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The flood-duration-frequency (QDF) analysis is performed using annual maximum streamflow series of 1–10 day durations observed at Pingshi and Lishi stations in southern China. The trends and change point of annual maximum flood flow and flood duration are also investigated by statistical tests. The results indicate that (1) the annual maximum flood flow only has a marginally increasing trend, whereas the flood duration exhibits a significant decreasing trend at the 0.10 significant level. The change point for the annual maximum flood flow series was found in 1991 and after which the mean maximum flood flow increased by 45.26%. (2) The period after 1991 is characterized by frequent and shorter duration floods due to increased rainstorm. However, land use change in the basin was found intensifying the increased tendency of annual maximum flow after 1991. And (3) under nonstationary environmental conditions, alternative definitions of return period should be adapted. The impacts on curve fitting of flood series showed an overall change of upper tail from “gentle” to “steep,” and the design flood magnitude became larger. Therefore, a nonstationary frequency analysis taking account of change point in the data series is highly recommended for future studies.
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Strupczewski, Witold G., Krzysztof Kochanek, Iwona Markiewicz, Ewa Bogdanowicz, Stanislaw Weglarczyk y Vijay P. Singh. "On the tails of distributions of annual peak flow". Hydrology Research 42, n.º 2-3 (1 de abril de 2011): 171–92. http://dx.doi.org/10.2166/nh.2011.062.
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This study discusses an application of heavy-tailed distributions to modelling of annual peak flows in general and of Polish data sets in particular. One- and two-shape parameter heavy-tailed distributions are obtained by transformations of random variables. The correct selection of a flood frequency model with emphasis on heavy-tailed distribution discrimination is then discussed. If a distribution is wrongly assumed, the error, in the upper quantile, arising as a result, depends on the method of parameter estimation and is shown analytically for three methods. Asymptotic and sampling values (got by simulation) were assessed for the pair log-Gumbel (LG) as a false distribution and log-normal (LN) as a true distribution. Comparing the upper quantiles of various distributions with the same values of moments, it is found that heavy-tailed distributions do not consistently provide higher flood frequency estimates than do soft-tailed distributions. Based on L-moment ratio diagrams and the test of linearity on log–log plots, it is concluded that Polish datasets of annual peak flows should be modelled using soft-tailed distributions, such as the three-parameter Inverse Gaussian, rather than heavy-tailed distributions.
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Hu, Kaiheng, Yong Li y Fangqiang Wei. "Annual risk assessment on high-frequency debris-flow fans". Natural Hazards 49, n.º 3 (20 de septiembre de 2008): 469–77. http://dx.doi.org/10.1007/s11069-008-9290-y.
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Pumo, D., F. Viola, G. La Loggia y L. V. Noto. "Annual flow duration curves assessment in ephemeral small basins". Journal of Hydrology 519 (noviembre de 2014): 258–70. http://dx.doi.org/10.1016/j.jhydrol.2014.07.024.
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Mizukami, Naoki, Oldrich Rakovec, Andrew J. Newman, Martyn P. Clark, Andrew W. Wood, Hoshin V. Gupta y Rohini Kumar. "On the choice of calibration metrics for “high-flow” estimation using hydrologic models". Hydrology and Earth System Sciences 23, n.º 6 (17 de junio de 2019): 2601–14. http://dx.doi.org/10.5194/hess-23-2601-2019.
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Abstract. Calibration is an essential step for improving the accuracy of simulations generated using hydrologic models. A key modeling decision is selecting the performance metric to be optimized. It has been common to use squared error performance metrics, or normalized variants such as Nash–Sutcliffe efficiency (NSE), based on the idea that their squared-error nature will emphasize the estimates of high flows. However, we conclude that NSE-based model calibrations actually result in poor reproduction of high-flow events, such as the annual peak flows that are used for flood frequency estimation. Using three different types of performance metrics, we calibrate two hydrological models at a daily step, the Variable Infiltration Capacity (VIC) model and the mesoscale Hydrologic Model (mHM), and evaluate their ability to simulate high-flow events for 492 basins throughout the contiguous United States. The metrics investigated are (1) NSE, (2) Kling–Gupta efficiency (KGE) and its variants, and (3) annual peak flow bias (APFB), where the latter is an application-specific metric that focuses on annual peak flows. As expected, the APFB metric produces the best annual peak flow estimates; however, performance on other high-flow-related metrics is poor. In contrast, the use of NSE results in annual peak flow estimates that are more than 20 % worse, primarily due to the tendency of NSE to underestimate observed flow variability. On the other hand, the use of KGE results in annual peak flow estimates that are better than from NSE, owing to improved flow time series metrics (mean and variance), with only a slight degradation in performance with respect to other related metrics, particularly when a non-standard weighting of the components of KGE is used. Stochastically generated ensemble simulations based on model residuals show the ability to improve the high-flow metrics, regardless of the deterministic performances. However, we emphasize that improving the fidelity of streamflow dynamics from deterministically calibrated models is still important, as it may improve high-flow metrics (for the right reasons). Overall, this work highlights the need for a deeper understanding of performance metric behavior and design in relation to the desired goals of model calibration.
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Venkataraman, Kartik, Narayanan Kannan y Victoria Chraibi. "Low Flow Trends in Texas Stream Segments Serving Unique Hydrologic Functions". Texas Water Journal 14, n.º 1 (20 de febrero de 2023): 3–33. http://dx.doi.org/10.21423/twj.v14i1.7143.
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In recognition of the unique hydrologic functions they serve, certain stream segments in Texas have been designated as ecologically significant. In this study, we evaluated low flow trends in seven hydrologically unique stream segments spanning three climatic divisions in Texas from 1970 to 2019. Despite increasing mean annual temperatures, there are no trends in low flows or other hydrologic variables in the East Fork of the San Jacinto River in the Upper Coast climatic division, likely due to local moisture surplus effects from the Gulf of Mexico. In the Edwards Plateau climatic division, annual low flows and annual baseflows are decreasing in the South Fork of the Guadalupe River, the Sabinal River and the Frio River. While increasing mean annual temperatures appear to have a role in the drying of all three of these stream segments, increasing annual potential evapotranspiration may be an additional driver in the Sabinal and Frio Rivers. Analysis of the Standardized Streamflow Index indicates that all seven stream segments experienced their worst streamflow droughts in the 2010s. As such, the watersheds draining to the gages on these stream segments have minimal anthropogenic impacts, suggesting the influence of climate on the observed stream drying.
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Piętka, Izabela. "Variability of Spring Riverflow of Selected Lowland Rivers". Miscellanea Geographica 14, n.º 1 (1 de diciembre de 2010): 177–83. http://dx.doi.org/10.2478/mgrsd-2010-0016.
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Abstract This paper aims at identification of changes in the spring discharge of six lowland rivers in Poland in 1966-2006. The contribution of the spring flow (February, March, April) in the annual flow was analysed as well as the 0.95 quantile time series of the daily flow. To investigate how the date of the occurrence of the spring riverflow changes, for each hydrological year the day up to which 50% of the annual flow had been reached was determined (CMD, the center of mass data). A test based on linear regression was applied, which determined the direction and rate of the changes. In five rivers, a statistically insignificant tendency to increase the contribution of the spring flow in the annual flow has been observed. A decreasing tendency in the spring discharge of all rivers has been shown; in two cases the changes are statistically significant. The tendencies in the CMD time series are not consistent.
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Benyahya, Loubna, Daniel Caissie, Fahim Ashkar, Nassir El-Jabi y Mysore Satish. "Comparison of the annual minimum flow and the deficit below threshold approaches: case study for the province of New Brunswick, Canada". Canadian Journal of Civil Engineering 36, n.º 9 (septiembre de 2009): 1421–34. http://dx.doi.org/10.1139/l09-077.
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A low-flow frequency analysis using the annual minimum flow (AMF) and the deficit below threshold (DBT) approaches was carried out for 30 hydrometric stations across the province of New Brunswick. The AMF method considers only the annual minimum events, and the DBT method considers all low flows below a certain threshold (or truncation level). In the present study, the DBT method characterizes low flow in terms of deficit intensity, which is becoming increasingly important in both water and aquatic resources management. The annual minimum series were fitted using the three-parameter Weibull distribution (AMF–WEI3), and the intensity data series were fitted using the two-parameter Weibull distribution (DBT–WEI2) and the generalized Pareto distribution (DBT–GP). All parameter estimates were obtained using the maximum likelihood method. The AMF–WEI3 and DBT–GP approaches provided a good fit to at-site data in terms of annual minimum flow and deficit intensity, respectively. However, the present study showed that the DBT–WEI2 approach underestimated the right tail of low-flow intensity. The Anderson–Darling statistic was also calculated for the data series and can provide insight into which distribution may adequately model the low-flow characteristics. A regionalization study was also performed using the AMF–WEI3 and DBT–GP methods.
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Alibaba, Halil. "Heat and Air Flow Behavior of Naturally Ventilated Offices in a Mediterranean Climate". Sustainability 10, n.º 9 (14 de septiembre de 2018): 3284. http://dx.doi.org/10.3390/su10093284.
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Air changes per hour (ach) rates for windows of different sizes and opened in different ratios were studied to establish natural ventilation concepts in offices with a Mediterranean climate. Dynamic thermal simulations were carried out in EDSL Tas for whole year investigations of an office. The office lost 0.01 W of heat during the winter but gained 0.01 W of heat during the summer. Annual average heat gain was 2.4 W. The heat gain via an external opaque wall was 138.9 W during the winter and 227.3 W during the summer, with an annual average of 190.7 W. The heat gain via an external glass surface was 128.9 W during the winter and 191 W during the summer, with an annual average of 161.5 W. The office had an average of 170.0 ach during the winter and an average of 144.7 ach during the summer, with an annual average of 157.4. The maximum annual ach performance was 480.4 ach when the external wall was fully glazed and the window was fully open, and the minimum annual ach performance was 9.8 when only 10% of the external wall was glass and 20% of the window area was open.
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Zhang, Ling, Jianzhong Lu, Xiaoling Chen, Dong Liang, Xiaokang Fu, Sabine Sauvage y José-Miguel Sanchez Perez. "Stream flow simulation and verification in ungauged zones by coupling hydrological and hydrodynamic models: a case study of the Poyang Lake ungauged zone". Hydrology and Earth System Sciences 21, n.º 11 (24 de noviembre de 2017): 5847–61. http://dx.doi.org/10.5194/hess-21-5847-2017.
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Abstract. To solve the problem of estimating and verifying stream flow without direct observation data, we estimated stream flow in ungauged zones by coupling a hydrological model with a hydrodynamic model, using the Poyang Lake basin as a test case. To simulate the stream flow of the ungauged zone, we built a soil and water assessment tool (SWAT) model for the entire catchment area covering the upstream gauged area and ungauged zone, and then calibrated the SWAT model using the data in the gauged area. To verify the results, we built two hydrodynamic scenarios (the original and adjusted scenarios) for Poyang Lake using the Delft3D model. In the original scenario, the upstream boundary condition is the observed stream flow from the upstream gauged area, while, in the adjusted scenario, it is the sum of the observed stream flow from the gauged area and the simulated stream flow from the ungauged zone. The experimental results showed that there is a stronger correlation and lower bias (R2 = 0.81, PBIAS = 10.00 %) between the observed and simulated stream flow in the adjusted scenario compared to that (R2 = 0.77, PBIAS = 20.10 %) in the original scenario, suggesting the simulated stream flow of the ungauged zone is reasonable. Using this method, we estimated the stream flow of the Poyang Lake ungauged zone as 16.4 ± 6.2 billion m3 a−1, representing ∼ 11.24 % of the annual total water yield of the entire watershed. Of the annual water yield, 70 % (11.48 billion m3 a−1) is concentrated in the wet season, while 30 % (4.92 billion m3 a−1) comes from the dry season. The ungauged stream flow significantly improves the water balance with the closing error decreased by 13.48 billion m3 a−1 (10.10 % of the total annual water resource) from 30.20 ± 9.1 billion m3 a−1 (20.10 % of the total annual water resource) to 16.72 ± 8.53 billion m3 a−1 (10.00 % of the total annual water resource). The method can be extended to other lake, river, or ocean basins where observation data is unavailable.
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Wakeyo, Fekremariam N., Assefa M. Melesse y Brook Abate. "Trends of Hydro-Meteorological Indices in Tendaho Catchment Part of Awash River Basin, Ethiopia". Environmental Sciences Proceedings 4, n.º 1 (13 de noviembre de 2020): 33. http://dx.doi.org/10.3390/ecas2020-08133.
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The variability in the intensity and frequency of extreme hydro-meteorological events due to climate change have an enormous impact on managing water resources in developing countries. Frequently it has been recognized as sudden droughts and severe floods. This study analyzed the spatial and temporal trends of five meteorology indices: annual maximum precipitation (AMP), annual precipitation (AP), mean areal precipitation (MAP), annual maximum temperature (AMaT) and annual minimum temperature (AMiT), and three streamflow indices: mean annual flow(MAF), annual maximum flow (AMaxF) and total mean annual flow (TMAF) over the Tendaho Catchment. Mann–Kendall (MK), Spearman Rho (SR), Sen’s slope (SS) test in R-program modifiedmk package, and Sen’s innovative trend test were used to detect trends of 16 meteorological and one streamflow stations from 1979–2017. The result showed that there is statistically significant temporal trends only in AMP, AP, AMaT, and AMiT at 6, 19, 56, and 50% of the stations respectively. The remaining indices have no statistically significant trend in all the stations. It also dictates that the catchment is characterized by a slightly increasing AP and AMP; a slightly decreasing MAP and significant increasing AMaT and AMiT trends. Except for AMaT, there is no particular spatial pattern of AP, MAP, and AMiT on the majority of the stations. Whereas, all streamflow indices showed a slightly decreasing temporal trend at 95% confidence. From this, we can conclude that the decreasing flow trend could be due to the decrement of MAP, an increment of temperature, and construction of reservoirs in the catchment.
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Wakeyo, Fekremariam N., Assefa M. Melesse y Brook Abate. "Trends of Hydro-Meteorological Indices in Tendaho Catchment Part of Awash River Basin, Ethiopia". Environmental Sciences Proceedings 4, n.º 1 (13 de noviembre de 2020): 33. http://dx.doi.org/10.3390/ecas2020-08127.
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The variability in the intensity and frequency of extreme hydro-meteorological events due to climate change have an enormous impact on managing water resources in developing countries. Frequently it has been recognized as sudden droughts and severe floods. This study analyzed the spatial and temporal trends of five meteorology indices: annual maximum precipitation (AMP), annual precipitation (AP), mean areal precipitation (MAP), annual maximum temperature (AMaT) and annual minimum temperature (AMiT), and three streamflow indices: mean annual flow(MAF), annual maximum flow (AMaxF) and total mean annual flow (TMAF) over the Tendaho Catchment. Mann–Kendall (MK), Spearman Rho (SR), Sen’s slope (SS) test in R-program modifiedmk package, and Sen’s innovative trend test were used to detect trends of 16 meteorological and one streamflow stations from 1979–2017. The result showed that there is statistically significant temporal trends only in AMP, AP, AMaT, and AMiT at 6, 19, 56, and 50% of the stations respectively. The remaining indices have no statistically significant trend in all the stations. It also dictates that the catchment is characterized by a slightly increasing AP and AMP; a slightly decreasing MAP and significant increasing AMaT and AMiT trends. Except for AMaT, there is no particular spatial pattern of AP, MAP, and AMiT on the majority of the stations. Whereas, all streamflow indices showed a slightly decreasing temporal trend at 95% confidence. From this, we can conclude that the decreasing flow trend could be due to the decrement of MAP, an increment of temperature, and construction of reservoirs in the catchment.
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SARMA, AALN, VVIZAYA BHASKAR y CM SASTRY. "Potential Evapotranspiration over India - An estimate of Green Water flow". MAUSAM 65, n.º 3 (1 de julio de 2014): 365–78. http://dx.doi.org/10.54302/mausam.v65i3.1042.
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The spatial distribution of Potential Evapotranspiration (PET) is studied by selecting stations that are drawn from the Koppen Climate spectrum of India that spread the length and breadth of the country using the modified Penman potential evapotranspiration equation. Annual and seasonal PET trends are reported. Variation of mean seasonal PET for the country as whole for all the four meteorological seasons and its rate of change are graphically shown. Anomalies in the annual and seasonal PET for the epoch of 1961-1995 with reference to the base period 1931-1960 are brought out. Distribution of climatic types over India according to Koppens climate classification for the period 1951-1980 are presented along with the changes that occurred compared to earlier report. Koppen climate types are characterized in terms of PET to P ratio expressed in percentage. Significant decreasing, increasing and no trend are noticed in annual PET both in space and time. Annual PET for the country as a whole is increased in the latter half of the 20th century. The mean seasonal potential evapotranspiration to precipitation ratio is found to be increased from tropical monsoon climates to dry climate types.
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Cockayne, B. J., D. Sternberg, D. W. Schmarr, A. W. Duguid y R. Mathwin. "Lake Eyre golden perch (Macquaria sp.) spawning and recruitment is enhanced by flow events in the hydrologically variable rivers of Lake Eyre Basin, Australia". Marine and Freshwater Research 66, n.º 9 (2015): 822. http://dx.doi.org/10.1071/mf14242.
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Understanding the links between fish recruitment and riverine flows is integral for setting priorities for river-management strategies, particularly in hydrologically variable and unpredictable arid and semi-arid zone rivers. In the present study, we used daily and annual otolith age estimates to identify relationships between riverine flow and spawning and recruitment of Lake Eyre golden perch (Macquaria sp.); an endemic fish of the Lake Eyre Basin, central Australia. We found a close association between Lake Eyre golden perch spawning and periods of increased river flow, with most of spawning occurring 0–35 days after the start of these flow events. Spawning occurred throughout the year but was commonly observed during the first flow events proceeding consecutive months of no-flow when water temperatures exceeded 26°C. Spawning was not dependent on floodplain inundation, with most spawning occurring during within-channel flow events. Annual average year-class strength was related to the number of flow events per year, but not total annual discharge, or the number of low-flow days per year. These results highlight the importance of natural within-channel flow patterns to Lake Eyre golden perch spawning and recruitment and demonstrate the importance of maintaining the natural flow regime of Australia’s arid- and semi-arid-zone rivers.
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Pastor, A. V., F. Ludwig, H. Biemans, H. Hoff y P. Kabat. "Accounting for environmental flow requirements in global water assessments". Hydrology and Earth System Sciences 18, n.º 12 (11 de diciembre de 2014): 5041–59. http://dx.doi.org/10.5194/hess-18-5041-2014.
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Abstract. As the water requirement for food production and other human needs grows, quantification of environmental flow requirements (EFRs) is necessary to assess the amount of water needed to sustain freshwater ecosystems. EFRs are the result of the quantification of water necessary to sustain the riverine ecosystem, which is calculated from the mean of an environmental flow (EF) method. In this study, five EF methods for calculating EFRs were compared with 11 case studies of locally assessed EFRs. We used three existing methods (Smakhtin, Tennant, and Tessmann) and two newly developed methods (the variable monthly flow method (VMF) and the Q90_Q50 method). All methods were compared globally and validated at local scales while mimicking the natural flow regime. The VMF and the Tessmann methods use algorithms to classify the flow regime into high, intermediate, and low-flow months and they take into account intra-annual variability by allocating EFRs with a percentage of mean monthly flow (MMF). The Q90_Q50 method allocates annual flow quantiles (Q90 and Q50) depending on the flow season. The results showed that, on average, 37% of annual discharge was required to sustain environmental flow requirement. More water is needed for environmental flows during low-flow periods (46–71% of average low-flows) compared to high-flow periods (17–45% of average high-flows). Environmental flow requirements estimates from the Tennant, Q90_Q50, and Smakhtin methods were higher than the locally calculated EFRs for river systems with relatively stable flows and were lower than the locally calculated EFRs for rivers with variable flows. The VMF and Tessmann methods showed the highest correlation with the locally calculated EFRs (R2=0.91). The main difference between the Tessmann and VMF methods is that the Tessmann method allocates all water to EFRs in low-flow periods while the VMF method allocates 60% of the flow in low-flow periods. Thus, other water sectors such as irrigation can withdraw up to 40% of the flow during the low-flow season and freshwater ecosystems can still be kept in reasonable ecological condition. The global applicability of the five methods was tested using the global vegetation and the Lund-Potsdam-Jena managed land (LPJmL) hydrological model. The calculated global annual EFRs for fair ecological conditions represent between 25 and 46% of mean annual flow (MAF). Variable flow regimes, such as the Nile, have lower EFRs (ranging from 12 to 48% of MAF) than stable tropical regimes such as the Amazon (which has EFRs ranging from 30 to 67% of MAF).
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Giles-Hansen, Krysta, Qiang Li y Xiaohua Wei. "The Cumulative Effects of Forest Disturbance and Climate Variability on Streamflow in the Deadman River Watershed". Forests 10, n.º 2 (22 de febrero de 2019): 196. http://dx.doi.org/10.3390/f10020196.
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Climatic variability and cumulative forest cover change are the two dominant factors affecting hydrological variability in forested watersheds. Separating the relative effects of each factor on streamflow is gaining increasing attention. This study adds to the body of literature by quantifying the relative contributions of those two drivers to the changes in annual mean flow, low flow, and high flow in a large forested snow dominated watershed, the Deadman River watershed (878 km2) in the Southern Interior of British Columbia, Canada. Over the study period of 1962 to 2012, the cumulative effects of forest disturbance significantly affected the annual mean streamflow. The effects became statistically significant in 1989 at the cumulative forest disturbance level of 12.4% of the watershed area. The modified double mass curve and sensitivity-based methods consistently revealed that forest disturbance and climate variability both increased annual mean streamflow during the disturbance period (1989–2012), with an average increment of 14 mm and 6 mm, respectively. The paired-year approach was used to further investigate the relative contributions to low and high flows. Our analysis showed that low and high flow increased significantly by 19% and 58%, respectively over the disturbance period (p < 0.05). We conclude that forest disturbance and climate variability have significantly increased annual mean flow, low flow and high flow over the last 50 years in a cumulative and additive manner in the Deadman River watershed.
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Pramono, I. B., T. M. Basuki y D. Auliyani. "Effect of rainfall on assessment of hydrologic sustainability in Citanduy sub-watersheds". IOP Conference Series: Earth and Environmental Science 1201, n.º 1 (1 de junio de 2023): 012032. http://dx.doi.org/10.1088/1755-1315/1201/1/012032.
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Abstract Hydrology is one of the criteria for monitoring and evaluation (monev) of watersheds management as stated in the Minister of Forestry Regulation Number P.61/Menhut-II/2014. So far, the use of various hydrological parameters for the monev of watersheds has not been evaluated whether these parameters truly reflect the condition of the watershed. This study aimed (1) to evaluate the effect of rainfall on the hydrological criteria of each sub-watershed, which include: flow regime coefficient, annual flow coefficient, sediment load, and water use index and (2) to evaluate the effect of rainfall on watershed carrying capacity. Regression analysis was used to see the relationship between annual rainfall and hydrological parameters used in watershed sustainability. This analysis was crucial to see the development of forest and land rehabilitation efforts in restoring degraded land. Data collection was carried out from 2008 to 2016 in each of the sub-watersheds of the Citanduy Watershed, namely Cijolang, Cikawung, Cimuntur, Ciseel, and Upper Citanduy. From this research, it is known that flow regime coefficient, annual flow coefficient, sediment load, water use index, and flood frequency are strongly influenced by rainfall so the result in evaluating watershed carrying capacity may vary depending on the rainfall. Besides being influenced by rainfall, flow regime coefficient, annual flow coefficient, and sediment load are also affected by land cover, while the slope affects the sediment load.
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Eiyubov, I. A. "CHANGES IN THE MONTHLY AND SEASONAL FLOW OF RIVERS IN AZERBAIJAN (OGUZ-GABALA DISTRICTS)". Geography and water resources, n.º 4 (28 de diciembre de 2023): 3–13. http://dx.doi.org/10.55764/2957-9856/2023-4-3-13.18.
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Azerbaijan (Oguz-Gabala region) was carried out. To assess current changes in water flow of rivers in the Oguz-Gabala region, statistical, water balance methods, as well as mathematical comparison methods were used. Average annual flows cover the period of observations of river flow from 1960 to 2017. The impact of modern changes on the regime of rivers in the Oguz-Gabala region has been assessed. The main goal of the work is to assess modern changes in river flow. River water flow for 1960-1990 (I period) was compared with water flow for 1991- 2017 (II period). Based on the results of comparing the average annual and average monthly flow rates of both periods, an assessment of changes in river flow was made.
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Wilkinson, Scott N., William J. Young y Ron C. DeRose. "Regionalizing mean annual flow and daily flow variability for basin-scale sediment and nutrient modelling". Hydrological Processes 20, n.º 13 (2006): 2769–86. http://dx.doi.org/10.1002/hyp.6070.
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Scott, Bill, Ross Lantzke, Dave Nicholson y Paul Findlater. "Comparison studies of unsaturated flow below annual and perennial plants". Water Science and Technology 65, n.º 12 (1 de junio de 2012): 2162–68. http://dx.doi.org/10.2166/wst.2012.116.
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Values of unsaturated water content determined with neutron moisture measurements (NMM) reveal different water profiles below different plantings. In the extremes, calibration requires a linear and logarithmic response (using the Lambert-W function) along with the normal submersion in a drum of water. Nevertheless a post-calibration with a hydraulic push sampler was used for confirmation. Data were collected at six pastures near the Western Australia coast near Geraldton, with four replicates through the profile. The sites have mostly sandy soils and receive 300–500 mm of rainfall annually. Findings generally showed that, if there was sufficient water, as in 2006, the perennials were able to use the water evenly throughout the vertical profile. Otherwise, with low rainfall, as in 2009, perennials struggle to survive and use less water than the annuals. Modelling of the soil water movement, plant growth and calibration/recalibration is and will be used to get a maximum likehood fit. Clearly, in desert conditions and little or no vegetation, rainfall tends to build up deep in the profile, increase salinity in groundwater, and create waterlogging. Any vegetation is helpful; perennials more so; provided they have sufficient water and are not significantly harvested.
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Li, X., RC Kellaway, RL Ison y G. Annison. "Digesta flow studies in sheep fed two mature annual legumes". Australian Journal of Agricultural Research 45, n.º 4 (1994): 889. http://dx.doi.org/10.1071/ar9940889.
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Mature subterranean clover (Trifolium subterraneum cv. Junee) and Persian clover (Trifolium resupinatum cv. Kyambro) were fed to cannulated sheep. Flow rates of dry matter and nitrogen in the abomasum and ileum were estimated using a double marker method. Contents of hemicellulosic polysaccharides (xylose and mannose monomers) were higher in Kyambro than in Junee. Although Junee contained higher levels of total N and amino acids, the relative concentrations of cystine and methionine were markedly higher in Kyambro. Dry matter intakes and flow rates in the abomasum, ileum and faeces were similar on Kyambro and Junee. Dietary nitrogen intake was lower and endogenous re-cycled nitrogen higher on Kyambro than on Junee. Ileal flow of nitrogen was similar to nitrogen intake on Kyambro. Apparent nitrogen digestibility was lower in the whole tract and higher in the intestines on Kyambro. The higher apparent digestibility of nitrogen in the intestines of sheep eating Kyambro was associated with a greater proportion of nitrogen leaving the stomach coming from endogenous sources. The lower nitrogen digestibility of Kyambro in the whole tract indicated lower digestibility of dietary nitrogen, which was associated with higher contents of xylose and mannose.
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Masliyah, J. H., Artin Afacan y Shijie Liu. "Flow through a Tube with an Annual Porous Medium Layer". Journal of Porous Media 8, n.º 2 (2005): 193–210. http://dx.doi.org/10.1615/jpormedia.v8.i2.70.
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Decker-Walters, D. S., T. W. Walters, U. Posluszny y P. G. Kevan. "Genealogy and gene flow among annual domesticated species of Cucurbita". Canadian Journal of Botany 68, n.º 4 (1 de abril de 1990): 782–89. http://dx.doi.org/10.1139/b90-104.
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Over the years, workers have gathered data from various sources in the attempt to understand the evolutionary histories and relationships of the domesticated members of Cucurbita. We used allozyme data to address questions of genealogy, interspecific gene flow, and allelic diversity for 23 commercial cultivars and 17 indigenous landraces of C. maxima, C. mixta, C. moschata, and C. pepo. Allelic diversity was greatest in C. pepo (especially ssp. ovifera) and C. moschata, reflecting complex histories for these taxa. Cucurbita maxima and C. mixta were relatively homogeneous despite morphological heterogeneity. Infraspecific classifications based on morphological characters were not supported by the allozyme data for C. maxima, C. mixta, and C. moschata. The allozymes supported morphological evidence of introgression from C. mixta in Oriental cultivars and southwestern United States and northwestern Mexico landraces of C. moschata. Phylogenetic analyses indicated that C. moschata and C. mixta are probably sister species and that C. pepo shares a common ancestor with these species that is not shared with C. maxima.
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Zhu, Yongxian, Kyle Syndergaard y Daniel R. Cooper. "Mapping the Annual Flow of Steel in the United States". Environmental Science & Technology 53, n.º 19 (30 de agosto de 2019): 11260–68. http://dx.doi.org/10.1021/acs.est.9b01016.
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Coward, Adrian V. y Philip Hall. "On the nonlinear interfacial instability of rotating core-annual flow". Theoretical and Computational Fluid Dynamics 5, n.º 6 (1993): 269–89. http://dx.doi.org/10.1007/bf00271423.
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Tsuda, Izumi, Kosuke Kurokawa y Ken Nozaki. "Annual simulation results of PV system with redox flow battery". Solar Energy Materials and Solar Cells 35 (11 de septiembre de 1994): 503–8. http://dx.doi.org/10.1016/0927-0248(94)90179-1.
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ISMAILOVA, I. G., G. KH ISMAIYLOV, L. D. RATKOVICH, N. V. MURASHCHENKOVA y A. V. PERMINOV. "ANALYSIS AND FORECAST OF RIVER WATERS IN THE VOLGA RIVER RUNOFF FORMATION ZONE BY THE TRENDS METHOD". Prirodoobustrojstvo, n.º 2 (2022): 69–78. http://dx.doi.org/10.26897/1997-6011-2022-2-69-78.
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The results of the study on the analysis, generalization and forecast of changes in the average annual and seasonal volumes (flows) of the Volga River to Volgograd (the formation zone) are presented. For the forecast, time flow series are used for the periods 1881/1882-2020/2021, N-140 years and 1914/1915/2020/2021, N-107 years. These periods are accepted as the basic periods characterizing the formation of the Volga River flow to Volgograd. It is revealed that the long-term fluctuations of the Volga River flow contain three periods, the first series, two periods, the second series, signifi cantly differing in average annual values. It is established that these periods under consideration are characterized, along with statistical long-term averages, by dynamic ones, which are functions in time. Also, the multidirectional trend (trends) in the considered flow time series are revealed. Functional equations for the identified trends for these periods are obtained. Thus, the presence of cycles and trends, in the long-term fluctuations of annual and seasonal values of river water infl ow, as well as functional equations serve as the scientific basis for their prediction for certain periods of time in the future, including the first half of the XXI century. The analysis based on sufficiently long time series of the river Volga to Volgograd shows that in the future there is a high probability of manifestation of different intensity of annual and seasonal flow due to its characteristic cyclical fluctuations. Confirmation of this, in particular, is the identification of changes in the nature of the trend of annual fluctuations in the flow of the Volga River in Volgograd.
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Xiong, Bin, Lihua Xiong, Jie Chen, Chong-Yu Xu y Lingqi Li. "Multiple causes of nonstationarity in the Weihe annual low-flow series". Hydrology and Earth System Sciences 22, n.º 2 (28 de febrero de 2018): 1525–42. http://dx.doi.org/10.5194/hess-22-1525-2018.
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Abstract. Under the background of global climate change and local anthropogenic activities, multiple driving forces have introduced various nonstationary components into low-flow series. This has led to a high demand on low-flow frequency analysis that considers nonstationary conditions for modeling. In this study, through a nonstationary frequency analysis framework with the generalized linear model (GLM) to consider time-varying distribution parameters, the multiple explanatory variables were incorporated to explain the variation in low-flow distribution parameters. These variables are comprised of the three indices of human activities (HAs; i.e., population, POP; irrigation area, IAR; and gross domestic product, GDP) and the eight measuring indices of the climate and catchment conditions (i.e., total precipitation P, mean frequency of precipitation events λ, temperature T, potential evapotranspiration (EP), climate aridity index AIEP, base-flow index (BFI), recession constant K and the recession-related aridity index AIK). This framework was applied to model the annual minimum flow series of both Huaxian and Xianyang gauging stations in the Weihe River, China (also known as the Wei He River). The results from stepwise regression for the optimal explanatory variables show that the variables related to irrigation, recession, temperature and precipitation play an important role in modeling. Specifically, analysis of annual minimum 30-day flow in Huaxian shows that the nonstationary distribution model with any one of all explanatory variables is better than the one without explanatory variables, the nonstationary gamma distribution model with four optimal variables is the best model and AIK is of the highest relative importance among these four variables, followed by IAR, BFI and AIEP. We conclude that the incorporation of multiple indices related to low-flow generation permits tracing various driving forces. The established link in nonstationary analysis will be beneficial to analyze future occurrences of low-flow extremes in similar areas.
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Dong, Qianjin, Debin Fang, Jian Zuo y Yongqiang Wang. "Hydrological alteration of the upper Yangtze River and its possible links with large-scale climate indices". Hydrology Research 50, n.º 4 (10 de abril de 2019): 1120–37. http://dx.doi.org/10.2166/nh.2019.112.
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Abstract The relationship between hydrological alteration and climate variability in the upper Yangtze River is not fully understood. In this paper, the periodicity features and the intercorrelation of annual and seasonal eco-flow metrics at the Yichang gauge station are analyzed for the period 1882 to 2013. Analysis is carried out to explore the formation of the eco-flow metrics and the possible linkages between eco-flow metrics and selected climate indices, using the cross-wavelet and wavelet coherence methods on data from 1948 to 2013. The results show that the variation of eco-flow metrics correlates well with some selected climate indices, but changes in different eco-flow metrics are complex. Most annual and seasonal eco-flow metrics correlate well with the Northern Hemisphere (N.H) and Indian Ocean Dipole (IOD) and have a significant common power in the two to four years band. In addition, most annual eco-flow metrics have an obvious phase relationship with the selected climate indices. However, the seasonal eco-flow metrics have no significant phase relationship with the selected climate indices. These findings provide a better understanding of how hydrological alterations of the streamflow and better water resource management can ensure ecosystem sustainability for the Yangtze River.