Streamflow alteration and habitat ramifications for a threatened fish species in the Central United States

In the Central United States, the Arkansas darter (Etheostoma cragini) is listed as a threatened fish species by the State of Kansas. Survival of the darter is threatened by loss of habitat caused by changing streamflow conditions, in particular flow depletion. Future management of darter populations and habitats requires an understanding of streamflow conditions and how those conditions may have changed over time in response to natural and anthropogenic factors. In Kansas, streamflow alteration was assessed at 9 U.S. Geological Survey streamgages in 6 priority basins with no pronounced long‐term trends in precipitation. The assessment was based on a comparison of observed (O) and predicted expected (E) reference conditions for 29 flow metrics. The O/E results indicated a likely or possible diminished flow condition in 2 basins; the primary cause of which is groundwater‐level declines resulting from groundwater pumping for irrigated agriculture. In these 2 basins, habitat characteristics adversely affected by flow depletion may include stream connectivity, pools, and water temperature. The other 4 basins were minimally affected, or unaffected, by flow depletion and therefore may provide the best opportunity for preservation of darter habitat. Through the O/E analysis, anthropogenic streamflow alteration was quantified and the results will enable better‐informed decisions pertaining to the future management of darters in Kansas.     

The Sanaga discharge at the Edea Catchment outlet (Cameroon): An example of hydrologic responses of a tropical rain‐fed river system to changes in precipitation and groundwater inputs and to flow regulation

The Sanaga River is one of Sub‐Saharan Africa's largest and greatly regulated rivers. Available flow data for this hydrosystem largely cover the pre‐ and post‐regulation periods. From comparisons between unregulated (hypothetical) and observed scenarios, it has been possible to separate and to quantify hydro‐climatic (groundwater + rainfall) change effects from anthropogenic impacts (especially dam‐related alterations). To appreciate shifts in the river regime, discontinuity detection tests and the IHA model were applied to discharge data series reflecting average and extreme flow conditions, respectively. Results obtained principally from the Hubert segmentation method reveal that a major discontinuity occurred in 1970–1971 separating a surplus phase between 1945–1946 and 1969–1970, and a deficient and much contrasted one, from 1971/1972. This implies that the Sanaga catchment is dominantly affected by hydro‐climatic changes. However, wide land cover/land use changes experienced here since 1988 have resulted in an increase in surface runoff. Additional quickflows linked to these changes may have partly compensated for the substantial decline in the dry season rainfall and groundwater inputs observed from this date. Although at the monthly scale, dam‐related impacts on average flows increase with stage of regulation, the seasonal variability of the river regime remains generally unaffected. A comparison of the IHA statistics, calculated from unregulated and observed streamflow data, show that hydrologic shifts occurring in maximum and minimum discharges are mostly significant from 1971/1972 and are mainly due to the action of dams. Minimum flows appear, however, widely impacted, thus reflecting the prime objective assigned to the existing reservoirs, constructed to supplement flows for hydroelectricity production during the dry season. Copyright © 2010 John Wiley & Sons, Ltd.     

Monthly Joint Operations for the Nakdong Multi-reservoir System in Korea

Abstract

This study applies a state-of-art optimization technique, SSDP/ESP (Sampling Stochastic Dynamic Programming with Ensemble Streamflow Prediction), to derive a monthly joint operating policy for the Nakdong multi-reservoir system in Korea. A rainfall-runoff model, SSARR (Streamflow Synthesis And Reservoir Regulation), is linked to the SSDP/ESP model to provide ESP scenarios for runoff during the next month in the Nakdong River basin. The primary advantage of the SSDP/ESP is that it updates the derived operating policy as new ESP forecasts become available. Another SSDP model that employs historical runoff scenarios (SSDP/Hist) is also developed. The main difference between the two SSDP models is that SSDP/Hist is an off-line model whereas the SSDP/ESP is on-line. The developed operating policies are tested with a simulation model using an object-oriented simulation software, STELLA. The simulation results show that SSDP/ESP is superior to SSDP/Hist with respect to the water supply criterion, although both models perform similarly with respect to the hydroelectric energy production criterion.     

An ARMA-type section model for average ten-day streamflow synthesis

Most of the rivers in Taiwan are short and run on a steep slope due to the island's topography. Because of the weak correlations of streamflow in time and the occurrence of extreme events such as typhoons, classical autoregressive-moving average (ARMA) models have difficulties in forecasting and synthesizing the average 10-day streamflow in Taiwan. In this study, the synthesis of the average 10-day streamflow of the Tanshui River in Taiwan is accomplished by a section model. The model divides the year-round streamflow records into several sections according to their distinguishable patterns, and each section is modeled by a separate ARMA model. For parameter control, a heuristic grouping procedure, based on statistical inference of the random noise part, is used to separate a year into a minimum number of sections. The section separation procedure follows the general precipitation pattern in a year. The case study results indicate high statistical agreement between synthesized series and historical records. Additionally, a new procedure, extended autocorrelation function (EACF), is introduced and applied in this study to assist in model identification.     

滇池入流径流模型

本文以松华坝、滇池两站模型为例，叙述了双变量模型的基本原理，建立了随机模型，模拟生成了径流系列，为滇池的水量及水质模拟模型提供了入流资料。     

影响水库径流调节的几个问题

文中从库容曲线的计算方法、供水保证率、蒸发和渗漏损失、调节时段等方面的问题,论述了各因素对调节计算及工程规模的影响,结合工程实例,提出在前期工作论证中加强基础资料的分析和整理,依据同类工程和技术规范,合理选取参数,为工程规模的合理论证提供科学、严谨、合理、准确的技术支撑。     

中国年径流频率分布及统计特征区域规律分析

基于全国514个水文站1956~2000年的年径流资料,采用线性矩比例图和线性矩-矩对比图分析了P-Ⅲ型分布、对数正态(LN)分布拟合我国多年平均年径流系列的情况,并利用强局部加权回归曲线(LOWESS)平滑散点数据进行分布函数拟合判断,表明P-Ⅲ分布对我国年径流资料适用性较好。基于此,对全国年径流统计特征和区域规律进行研究,建立了南北分区径流量(深)、流域面积、标准差、离散系数之间的经验关系,为水资源规划及合理开发利用提供了依据。     

Effects of climate change and anthropogenic activities on runoff change of the Weihe River basin,Northwest China

The Weihe River has experienced a significant runoff decline in the past few decades, but the detailed and systematic analysis of different sub-regions of the Weihe River basin (WRB) for a long time is insufficient. Based on the data of five hydrological stations from 1957 to 2018, this study investigated the variation of annual runoff both in the whole Weihe River basin (WWRB) and its sub-regions: the upper, middle, and lower reaches of the Weihe River (URWR, MRWR, LRWR, respectively), the Jing River basin (JRB), and the Beiluo River basin (BLRB). Moreover, the contribution of climate change and anthropogenic activities on runoff change was quantified by double mass curve (DMC) and hydrological sensitivity analysis (HSA) methods. The results showed that runoff of the URWR, MRWR, JRB, BLRB, and WWRB showed significant downward trends, and with the change-point years of 1993, 1990, 1996, 1994, and 1993, respectively. Both results of DMC and HSA showed that anthropogenic activities were the main factors for runoff reduction. The contribution of human activities was largest in the JRB and BLRB, whereas lowest in the MRWR. Over the study period, land use has changed significantly in the basin, mainly manifested in the reduction of farmland, and the increase of construction land and grassland, indicating that intense anthropogenic activities have taken place. Moreover, the total water consumption of the WWRB increased evidently, which exacerbated the contradiction between supply and demand of water resources. The results of HSA showed that runoff was more sensitive to precipitation than to E_p. Precipitation reduced the runoff, while E_p increased runoff in the basin. The results of this study are helpful for understanding the regional hydrological situation in more detail, and can act as a reference for formulating reasonable water resources allocation schemes.     

Extreme value analysis of streamflow time series in Poyang Lake Basin, China

Extreme meteorological and hydrological events may cause major disasters and heavy social and economic losses.Therefore,more and more studies have focused on extreme hydro-meteorological events in various climates and geographic regions.Based on nearly 50 years of observed records of the Poyang Lake Basin,the occurrence and changing trends of extreme streamflow indices,including the annual maximum flow,annual peak-over-threshold flows,and low flows,were analyzed for ten hydrological stations.The results indicate that most annual maximum flows occurred from April to July,highly attributed to the Southeast Asian summer monsoons,whereas the annual minimum flows were concentrated between January and February.As for the low flow indices (the annual minimum flow,annual minimum 7-d flow,and annual minimum 30-d flow),a significant increasing trend was detected in most parts of the Poyang Lake Basin.The trends illustrate the potential effects of climate change and human activities on the hydrological cycle over the Poyang Lake Basin.     

青藏高原东南部径流特征的空间规律及控制因子研究

采用青藏高原东南部的水文气象资料,对比分析了该地区23个(区间)流域的年径流深、集中度与集中期、基流系数、退水系数等径流特征及其空间分布规律,并进一步研究了这些径流特征的控制因子。结果表明:该地区径流特征的空间分布规律为年径流深从东南(700~1 300 mm)向西北(<400 mm)递减,而集中度则呈相反的空间格局(从<0.44增加到>0.59);退水系数及基流系数,在低海拔地区随高程增大而增大(分别为0.55~0.69、0.51~0.73),但在高海拔地区则随高程增大而减小(0.74~0.42、0.79~0.63)。本研究发现,青藏东南径流特征空间规律的控制因子,具有显著的区域分异:在低海拔流域(平均高程<3 000 m),降水是径流特征的主要影响因子;而在高海拔流域(平均高程>3 000 m),仅径流深和集中度受降水控制,其他特征则主要受温度、冻土、地形等条件的共同影响。可见,由于青藏高原东南部降水和冻土对气候变化敏感,该地区水资源时空分布格局将面临很大的不确定性,对此应予以充分重视。