Estimation of Daily Streamflow of Southeastern Coastal Plain Watersheds by Combining Estimated Magnitude and Sequence

Commonly used methods to predict streamflow at ungauged watersheds implicitly predict streamflow magnitude and temporal sequence concurrently. An alternative approach that has not been fully explored is the conceptualization of streamflow as a composite of two separable components of magnitude and sequence, where each component is estimated separately and then combined. Magnitude is modeled using the flow duration curve (FDC), whereas sequence is modeled by transferring streamflow sequence of gauged watershed(s). This study tests the applicability of the approach on watersheds ranging in size from about 25‐7,226 km² in Southeastern Coastal Plain (U.S.) with substantial surface storage of wetlands. A 19‐point regionalized FDC is developed to estimate streamflow magnitude using the three most selected variables (drainage area, hydrologic soil index, and maximum 24‐h precipitation with a recurrence interval of 100 years) by a greedy‐heuristic search process. The results of validation on four watersheds (Trent River, North Carolina: 02092500; Satilla River, Georgia: 02226500; Black River, South Carolina: 02136000; and Coosawhatchie River, South Carolina: 02176500) yielded Nash‐Sutcliffe efficiency values of 0.86‐0.98 for the predicted magnitude and 0.09‐0.84 for the predicted daily streamflow over a simulation period of 1960‐2010. The prediction accuracy of the method on two headwater watersheds at Santee Experimental Forest in coastal South Carolina was weak, but comparable to simulations by MIKE‐SHE.     

A Two‐Decade Watershed Approach to Stream Restoration Log Jam Design and Stream Recovery Monitoring: Finney Creek,Washington

A federal, state, and private partnership leveraged resources and employed a long‐term, systematic approach to improve aquatic habitat degraded by decades of intensive forest management in Finney Creek, a tributary to the Skagit River of Northwest Washington State. After more than a decade of work to reduce sediment sources and the risk of landslides within the watershed, log jam installation commenced in 1999 and progressed downstream through 2010. Log jam design was adapted as experience was gained. A total of 181 log jams, including 60 floating log ballasted jams, were constructed along 12 km of channel. The goal was to alter hydraulic processes that affect aquatic habitat formation along 39 km of stream with emphasis on 18.5 km of lower Finney Creek. Aquatic habitat surveys over a five‐year period show an increase in the area of large pools and an accompanying increase in residual and maximum pool depth in the lower river reach. Channel cross sections show a generally deeper channel at the log jams, better channel definition in the gravel deposits at the head of the log jams, and improved riffle and thalweg development below the log jams. Stream temperature in the upper river decreased by 1.0°F in the first three years, and 1.1°F in the lowest treated reach over nine years. There is a trend of less stream heating over the restoration time period. Photo points show that riparian vegetation is recolonizing gravel bars.     

The role of community-based watershed development in reducing farmers’ vulnerability to climate change and variability in the northwestern highlands of Ethiopia

ABSTRACT

Community-based watershed development (CBWD) has been implemented in Ethiopia since the last three decades. However, the benefits of these watershed development interventions for climate change adaptation are not well documented. This study, therefore, assesses the contributions of CBWD in reducing farmers’ vulnerability to the impacts of climate change and variability in the northwestern highlands of Ethiopia. Data were collected from systematically selected 157 households using questionnaire. The questionnaire consists of questions on climate, ecosystem and households’ livelihood capital. Livelihood Vulnerability Index (LVI) and Inter-governmental Panel on Climate Change Livelihood Vulnerability Index (IPCC-LVI) methods were used to generate vulnerability indices. Vulnerability indices computed for three conserved watersheds were compared with one non-conserved watershed using one-way ANOVA test. LVI score for ecosystem related indicators was significantly low for Adef Wuha compared to the non-conserved watershed. Similarly, LVI scores generated from agriculture, wealth and social indicators were low for Tija Baji and Guansa watersheds. On the other hand, the IPCC-LVI result did not show significant differences in exposure; however, sensitivity scores of conserved watersheds were significantly lower compared to the non-conserved. The adaptive capacities of two conserved watersheds (Guansa and Tija Baji) were also significantly lower as compared to the non-conserved. The overall (composite) vulnerability of watersheds generated from both methods (LVI and IPCC-LVI) showed that the conserved watersheds were less vulnerable to climate change compared to the non-conserved. The findings suggest that CBWD is an important strategy to reduce vulnerability of smallholder farmers to the ongoing and future climate change.     

一个新的分布式水文模型在鄱阳湖赣江流域的验证

考虑同类模型在模拟大尺度流域时存在的一些弱点，开发了基于单元网格，并且结构较为简单、参数数量较少的分布式水文模型WATLAC。为了验证该模型在大尺度流域长时间序列的模拟效果，选取鄱阳湖流域的最大子流域——赣江流域（817万km2）为验证区域。流域的空间非均匀性由单元网格离散并模拟。根据下垫面数据精度，选取4 km×4 km的离散网格尺寸，并应用ArcGIS等软件建立流域网格信息，生成模型输入数据。采用1960~1989年外洲站和峡江站的实测资料对模型进行了验证。率定期（1960~1969年）两水文站日、月和年径流确定性系数在081~093，Ens系数在079~099，年径流统计量相对误差均低于8%；校核期（1970~1989年）两水文站日、月和年径流确定性系数在076~092，Ens系数在075~091，年径流统计量相对误差均低于2%。结果显示，模拟的径流量与实测值吻合良好，模型在赣江流域得到了很好的验证。模型对赣江流域具有较强的适用性，在流域水资源管理中具有较好的应用前景。     

MANAGEMENT OF BASEFLOW AUGMENTATION: A REVIEW1

ABSTRACT: Baseflow augmentation refers to the temporary storage of subsurface water in floodplains, streambanks, and/or stream bottoms during the wet season, either by natural or artificial means, for later release during the dry season to increase the magnitude and permanence of low flows. Management strategies for baseflow augmentation fall into the following categories: (1) range management, (2) upland vegetation management, (3) riparian vegetation management, (4) upland runoff detention and retention, and (5) the use of instream structures. The benefits of a management strategy focused on baseflow augmentation are many, including: (1) increased summer flows, (2) healthier riparian areas, (3) increased channel and bank stability, (4) decreased erosion and sediment transport, (5) improved water quality, (6) enhanced fish and wildlife habitat, (7) lower stream temperatures, and (8) improved stream aesthetics. This review has shown that baseflow augmentation has been successfully accomplished in a few documented cases. Given its clear impact on soil and water conservation, particularly in the semiarid western U.S., it appears that baseflow augmentation is a concept whose time has come. Research is needed on how to successfully integrate baseflow augmentation within comprehensive resource management strategies.     

NUTRIENT CONTRIBUTION OF NONPOINT SOURCE RUNOFF IN THE LAS VEGAS VALLEY1

ABSTRACT: A Geographic Information System (GIS) based non‐point source runoff model is developed for the Las Vegas Valley, Nevada, to estimate the nutrient loads during the years 2000 and 2001. The estimated nonpoint source loads are compared with current wastewater treatment facilities loads to determine the non‐point source contribution of total phosphorus (TP), total nitrogen (TN), and total suspended solids (TSS) on a monthly and annual time scale. An innovative calibration procedure is used to estimate the pollutant concentrations for different land uses based on available water quality data at the outlet. Results indicate that the pollutant concentrations are higher for the Las Vegas Valley than previous published values for semi‐arid and arid regions. The total TP and TN loads from nonpoint sources are approximately 15 percent and 4 percent, respectively, of the total load to the receiving water body, Lake Mead. The TP loads during wet periods approach the permitted loads from the wastewater treatment plants that discharge into Las Vegas Wash. In addition, the GIS model is used to track pollutant loads in the stream channels for one of the subwatersheds. This is useful for planning the location of Best Management Practices to control nonpoint pollutant loads.     

The State of Protected Forest Communities in the European Forest–Steppe Zone of Russia and Prospects for Their Reconstruction: A Case Study of Specially Protected Areas of Penza Oblast

The structure of most forest communities in the European forest–steppe, including protected areas, has been disturbed. The adverse consequences of these disturbances include the incomplete age structure of the populations of cenosis-forming species and the irreversibility of successions. The conservation of biodiversity in the structurally disturbed communities is impossible without human intervention, which must be aimed at restoring their age heterogeneity with regard to their specific ecological features.     

HYDROLOGIC LANDSCAPES ON THE DELMARVA PENINSULA PART 2: ESTIMATES OF BASE-FLOW NITROGEN LOAD TO CHESAPEAKE BAY1

ABSTRACT: Base-flow samples were collected from 47 sampling sites for four seasons from 1990–91 on the Delmarva Peninsula in Delaware and Maryland to relate stream chemistry to a “hydrologic landscape” and season. Two hydrologic landscapes were determined: (1) a well-drained landscape, characterized by a combination of a low percentage of forest cover, a low percentage of poorly drained soil, and elevated channel slope; and (2) poorly drained landscape, characterized by a combination of an elevated percentage of forest cover, an elevated percentage of poorly drained soil, and low channel slope. Concentrations of nitrogen were significantly related to the hydrologic landscape. Nitrogen concentrations tended to be higher in well-drained landscapes than in poorly drained ones. The highest instantaneous nitrogen yields occurred in well-drained landscapes during the winter. These yields were extrapolated over the part of the study area draining to Chesapeake Bay in order to provide a rough estimate of nitrogen load from base flow to the Bay and its estuarine tributaries. This estimate was compared to an estimate made by extrapolating from an existing long-term monitoring station. The load estimate from the stream survey data was 5 ± 10⁶ kg of N per year, which was about four times the estimate, made from the existing long-term monitoring station. The stream-survey estimate of base flow represents about 40 percent of the total nitrogen load that enters the Bay and estuarine tributaries from all sources in the study area.     

青海湖流域生态安全评价

进行流域的生态安全评价,对于改善流域的生态环境,维护区域的可持续发展具有重要 的意义。本文选择自然生态环境状态指数、人文社会压力指数、环境破坏压力指数,构建了青海 湖流域生态安全综合评价指数模型,提取了生态安全指标,对2000 年青海湖流域的生态安全进 行了评价。结果表明,2000 年青海湖流域生态安全属于生态安全预警等级,流域生态安全面临着 较为严峻的挑战。气候变化和人类活动对青海湖流域的生态环境产生的负效应,也因此会影响到 区域的可持续发展,所以必须进行流域的综合治理,改善当地的生态环境。     

日本湖泊水质富营养化控制措施与政策

日本在经历了20世纪50年代和60年代的严重污染事件后,强化了环境政策.在水污染控制法中从严制定了污水排放限制和水质标准,在20世纪70年代和80年代成功地减少了污染.对"日本湖泊水质保全特别措施法"的现状、流域的点源和非点源污染负荷的削减、湖泊底泥的疏浚以及采用生态工程方法减少支流负荷等流域综合管理进行了综述和探讨,并给出了进一步改善湖泊水质的建议.