Curve Number Derivation for Watersheds Draining Two Headwater Streams in Lower Coastal Plain South Carolina,USA

The objective of this study was to assess curve number (CN) values derived for two forested headwater catchments in the Lower Coastal Plain (LCP) of South Carolina using a three‐year period of storm event rainfall and runoff data in comparison with results obtained from CN method calculations. Derived CNs from rainfall/runoff pairs ranged from 46 to 90 for the Upper Debidue Creek (UDC) watershed and from 42 to 89 for the Watershed 80 (WS80). However, runoff generation from storm events was strongly related to water table elevation, where seasonally variable evapotranspirative wet and dry moisture conditions persist. Seasonal water table fluctuation is independent of, but can be compounded by, wet conditions that occur as a result of prior storm events, further complicating flow prediction. Runoff predictions for LCP first‐order watersheds do not compare closely to measured flow under the average moisture condition normally associated with the CN method. In this study, however, results show improvement in flow predictions using CNs adjusted for antecedent runoff conditions and based on water table position. These results indicate that adaptations of CN model parameters are required for reliable flow predictions for these LCP catchments with shallow water tables. Low gradient topography and shallow water table characteristics of LCP watersheds allow for unique hydrologic conditions that must be assessed and managed differently than higher gradient watersheds.     

近25年雅鲁藏布江中游蒸发皿蒸发量及其影响因素的变化

采用气候倾向率方法,对西藏雅鲁藏布江(下称"雅江")中游1981~2005年14个气象站年、季小型蒸发皿蒸发量及其影响气候因子的变化趋势进行了分析。结果表明:近25年西藏雅江中游年蒸发皿蒸发量在流域绝大部分站点均呈现显著的减少趋势,平均减幅为109.92mm,以夏季减少趋势最明显。影响蒸发皿蒸发量的主要气候因子日照时数、平均风速呈现显著下降趋势,平均相对湿度、降水量表现为显著增加,平均气温显著升高,平均最低气温的升温速率(0.52℃/10a)明显比平均最高气温的升温速率(0.23℃/10a)大,导致气温日较差减少(-0.29℃/10a)。因此,雅江中游年日照时数和平均风速的显著下降,以及年平均相对湿度的明显增加可能是年蒸发皿蒸发量显著下降的主要原因,平均气温日较差的显著减小和降水量的增加在蒸发量减少趋势中的作用也不可忽视。     

惠阳城区降雨径流重金属污染特征研究：Ⅰ.地表堆积物重金属含量分析

以惠阳城区为研究对象,选取4种具有代表性的典型城市功能区类型:工业区、商业区、住宅区、交通区,对其地表堆积物进行样品采集和实验分析.结果表明:地表堆积物细粒部分(粒径<149舯)所占比例为51%,粗粒部分(粒径>2 000um,)所占比例仅4.1%;重金属含量的粒径分级特性和质量分数相似,即粒径越细的部分重金属含量越高;Pb,Zn,Cu.Cr之间的相关系数较高;重金属的浸出浓度在不同的功能区基本遵循同样的规律,即细粒部分重金属浸出浓度最高,随粒径的增大浸出浓度逐减,细粒部分重金属的浸出浓度:w(Pb)为59.1 rag/kg/kg,w(Zn)为93.5 mg/kg,w(Cu)为37.7 ms/ks,w(Cr)为23.9 ms/kg,w(Cd)为0.07 mg,kg.     

Runoff variation affected by precipitation change and human activity in Hailiutu River basin,China

For recent years, runoff generation and hydrological processes in Hailiutu River basin have been greatly changed by climate change and human activity, especially water and soil conservation construction. In this study, the trends in precipitation, evapotranspiration (ET) and river runoff as well as the effects of precipitation change and human activity on runoff variation have been studied. The results showed that during 1960–2000, annual precipitation and river runoff, monthly precipitation and ET in September and October as well as monthly runoff in all months showed a significant decrease. In addition, peak flow and base flow had a large decrease. Under the joint influence of precipitation change and human activity, the mean annual runoff decreased by 35 million m³ from the baseline period (1960–1985) to the change period (1986–2000), which accounted for 60.9% and 39.1% of the total runoff decrease, respectively. Precipitation change played a primary role in the decrease of annual runoff whereas human activity, particularly water and soil conservation construction, also had remarkable impacts on runoff variation.     

不同土地利用方式土壤表层氮、磷流失特征研究

利用室内人工模拟降雨,选择徐州沛沿河流域3种典型土地利用类型,研究了不同土地利用下土壤表层N、P随降雨径流的迁移过程.研究结果表明,在相同降雨条件下,3种土地产流量大小顺序为稻田地〉林地〉果园,产泥沙量大小顺序为果园〉稻田地〉林地.降雨径流水相中TN、TP浓度呈现随降雨时间的持续显著下降,然后逐渐稳定的趋势,氮磷的流失...     

Hydrologic and Phosphorus Export Behavior of Small Streams in Commercial Poultry‐Pasture Watersheds1

Romeis, J. Joshua, C. Rhett Jackson, L. Mark Risse, Andrew N. Sharpley, and David E. Radcliffe, 2011. Hydrologic and Phosphorus Export Behavior of Small Streams in Commercial Poultry‐Pasture Watersheds. Journal of the American Water Resources Association (JAWRA) 1‐19. DOI: 10.1111/j.1752‐1688.2011.00521.x Abstract: Few watershed‐scale studies have evaluated phosphorus export in streamflow from commercial poultry‐pasture operations. Continuous streamflow and mixed‐frequency water quality datasets were collected from nine commercial poultry‐pasture (AG) and three forested (FORS) headwater streams (2.4‐44 ha) in the upper Etowah River basin of Georgia to estimate total P (TP) loads and examine variability of hydrologic response and water quality of storm and nonstorm‐flow regimes. Data collection duration ranged from 18 to 22 months, and approximately 1,600 water quality samples were collected. Significant (p < 0.1) inverse relationships were detected between peak flow response variables and both drainage area and fraction of forest cover. Order‐of‐magnitude differences in TP and dissolved reactive P (DRP) concentration were observed between AG and FORS sites and among AG sites. TP yields of FORS sites ranged from 0.01 to 0.1 kg P/ha. Yields of AG sites ranged from 0.031 to 3.17 kg P/ha (median = 0.354 kg P/ha). With 95% confidence intervals, AG yields ranged from 0.025 to 13.1 kg P/ha. These small‐watershed‐scale yields were similar to field‐scale yields measured in other studies in other regions. TP yields were significantly related to area‐weighted Mehlich‐1 soil test P concentrations (p = 0.0073) and base‐flow water sample P concentrations (p ≤ 0.0005). Water quality sampling during base‐flow conditions may be a useful screening tool for P risk‐based management programs.     

Using a GIS Model to Identify Internally Drained Areas and Runoff Contribution in a Glaciated Watershed1

Macholl, Jacob A., Katherine A. Clancy, and Paul M. McGinley, 2011. Using a GIS Model to Identify Internally Drained Areas and Runoff Contribution in a Glaciated Watershed. Journal of the American Water Resources Association (JAWRA) 47(1):114‐125. DOI: 10.1111/j.1752‐1688.2010.00495.x Abstract: Glaciated watersheds are not easily delineated using geographic information systems’ elevation‐based algorithms, especially where stream networks are disconnected and there are large regions of internally drained areas. This paper presents the results of an analysis using the Potential Contributing Source Area (PCSA) model to identify potential contributing areas, defined as areas from which runoff is physically capable of reaching a drainage network. The investigation was conducted to define the potential contributing areas in a glaciated region of northwest Wisconsin. The curve number (CN) method was used to predict runoff volumes in the watershed. The streamflows of four tributaries were measured and the runoff portion of the hydrograph quantified to be compared with runoff estimates calculated using the potential contributing areas and the traditional catchment area. Runoff producing events occurred, but the use of area‐weighted CN values was unsuccessful in modeling runoff due to all precipitation depths during the study period falling below the initial abstraction. A distributed CN approach provided runoff estimates that were generally better using the potential contributing areas compared with using the traditional catchment area. The extent of the minimum contributing area, estimated for a range of precipitation events, was found to be substantially less than the potential contributing areas, suggesting that the PCSA model delimits the maximum boundary of potential contributing areas.     

A Perspective on Nonstationarity and Water Management1

Hirsch, Robert M., 2011. A Perspective on Nonstationarity and Water Management. Journal of the American Water Resources Association (JAWRA) 47(3):436‐446. DOI: 10.1111/j.1752‐1688.2011.00539.x Abstract: This essay offers some perspectives on climate‐related nonstationarity and water resources. Hydrologists must not lose sight of the many sources of nonstationarity, recognizing that many of them may be of much greater magnitude than those that may arise from climate change. It is paradoxical that statistical and deterministic approaches give us better insights about changes in mean conditions than about the tails of probability distributions, and yet the tails are very important to water management. Another paradox is that it is difficult to distinguish between long‐term hydrologic persistence and trend. Using very long hydrologic records is helpful in mitigating this problem, but does not guarantee success. Empirical approaches, using long‐term hydrologic records, should be an important part of the portfolio of research being applied to understand the hydrologic response to climate change. An example presented here shows very mixed results for trends in the size of the annual floods, with some strong clusters of positive trends and a strong cluster of negative trends. The potential for nonstationarity highlights the importance of the continuity of hydrologic records, the need for repeated analysis of the data as the time series grow, and the need for a well‐trained cadre of scientists and engineers, ready to interpret the data and use those analyses to help adjust the management of our water resources.     

变化环境下北江下游年径流量的加权马尔可夫链预测

在气候变化和人类活动的影响下,西北江的水文环境发生了重大变化,导致北江下游的来水条件发生变化。采用斯波曼检验（Spearman’s rho test）和Mann-kendall法系统地分析了北江下游的年径流量的变化趋势和变异情况,在此基础上建立了北江下游变化环境下年径流量的加权马尔可夫链预测模型。结果表明：西北江近50年来的大规模联围筑闸、大规模无序采掘河床泥沙等剧烈的人类活动,导致北江下游三水水文站年径流量在1990年左右发生了变异;所建立的加权马尔可夫链预测结果表明,从变异后的序列中统计出来的状态＂转移概率＂矩阵,能准确地反映出环境变化后年径流量之间的关系,所建立的加权马尔可夫链法预测变化环境下的年径流量是可行的,预测效果也比较好;按文章确定的分级标准,依现有的资料信息推断,环境发生变化后,在未来长期过程中,北江下游出现平水年的机会最大,但年际间的丰枯波动概率也不小。这一结果值得水资源管理部门注意。     

基于洪水演进数值模拟的溃坝危害性快速评估

采用部分溃坝模型与堰流相交算法计算溃坝最大流量,并基于四次抛物线概化方法得到溃坝洪水的流量过程线;利用洪峰展平法将洪水波概化为三角形,对洪水演进过程进行模拟,分析溃口宽度和溃口形态对洪水演进过程的影响;研究考虑不同溃坝条件下对溃坝洪水的到时、最大流量、水深和洪水历时等洪水演进的主要参数的快速估算方法,以实现对地震可能引发不同溃坝事件危害性的快速评估。