基于RUSLE模型的延河流域2001-2010年土壤侵蚀动态变化

以黄土高原典型丘陵沟壑区--延河流域为研究区, 基于GIS和RS技术, 利用2001-2010年延河流域水文站月降雨量数据、MODIS NDVI数据、DEM数据、土壤类型数据和土地利用数据,率定了修正的通用土壤流失方程(RUSLE)的相关参数,计算了研究区2001-2010年逐年的土壤侵蚀模数, 利用杏河水文站实测的泥沙数据, 验证了模型的有效性,分析了延河流域土壤侵蚀强度的时空变化特征。结果表明,2001年到2010年延河流域土壤侵蚀模数呈减小趋势,2001年土壤侵蚀模数最大,为6 596.72 t/(km²·a),2008年土壤侵蚀模数最小,减小到2 485.46 t/(km²·a),降低62.32%;2009年由于暴雨冲刷,土壤侵蚀模数显著增大;2010年土壤侵蚀模数和2006、2007年相差不多;土壤侵蚀强度分布比例变化明显,土壤侵蚀强度为强度、极强、剧烈的面积比分别由16.21%、21.93%和12.36%降低为10.85%、4.58%和0.39%。土壤侵蚀强度等级转移矩阵表明大部分地区的土壤侵蚀强度向低一级转移,2001-2005年31.68%的面积土壤侵蚀强度降低一级,2005-2010年42.13%的面积土壤侵蚀强度降低一级。     

Lessons for successful participatory watershed modeling: A perspective from modeling practitioners

Participatory modeling is the process of incorporating stakeholders, often including the public, and decision makers into an otherwise purely analytic modeling process to support decisions involving complex natural resources questions. Participatory modeling is particularly compatible with the rising focus on integrated water resources management, which incorporates systems theory and aims to protect and improve water resources while considering economic and social concerns in the community. In this article, we present a series of lessons based on experience working with stakeholder groups to develop watershed and water quality models to address water resource issues in Maryland, Vermont, Utah, and Virginia. We believe these lessons in participatory modeling, discussed from our perspective as scientists and modelers engaged in applied watershed issues, can help to achieve successful participatory modeling efforts elsewhere. The lessons relate to stakeholder engagement, modeling tools, model development and calibration, scenario testing, and applying results to management decisions.     

Integrating sentinel watershed-systems into the monitoring and assessment of Minnesota’s (USA) waters quality

Section 303(d) of the Clean Water Act requires States and Tribes to list waters not meeting water quality standards. A total maximum daily load must be prepared for waters identified as impaired with respect to water quality standards. Historically, the management of pollution in Minnesota has been focused on point-source regulation. Regulatory effort in Minnesota has improved water quality over the last three decades. Non-point source pollution has become the largest driver of conventional 303(d) listings in the 21st century. Conventional pollutants, i.e., organic, sediment and nutrient imbalances can be identified with poor land use management practices. However, the cause and effect relationship can be elusive because of natural watershed-system influences that vary with scale. Elucidation is complex because the current water quality standards in Minnesota were designed to work best with water quality permits to control point sources of pollution. This paper presents a sentinel watershed-systems approach (SWSA) to the monitoring and assessment of Minnesota waterbodies. SWSA integrates physical, chemical, and biological data over space and time using advanced technologies at selected small watersheds across Minnesota to potentially improve understanding of natural and anthropogenic watershed processes and the management of point and non-point sources of pollution. Long-term, state-of-the-art monitoring and assessment is needed to advance and improve water quality standards. Advanced water quality or ecologically-based standards that integrate physical, chemical, and biological numeric criteria offer the potential to better understand, manage, protect, and restore Minnesota’s waterbodies.     

辽河流域水环境监测网络优化技术研究

以辽河流域2009—2011年监测数据为基础,针对北方季节性河流,在制定了水环境监测网络优化原则的前提下,分别运用最优分割法、变异系数与水质类别相结合方法、连续3年未检出判断法进行了辽河流域水环境质量监测断面、监测频次和监测项目的优化。结果表明,辽河流域优化后的监测断面为18个,比优化前减少8个。在监测频次上,干旱少雨的月份中,1、5、10月应保持每个月2次的监测频次,2—4月、11—12月每月监测1次;湿润多雨的6—9月只监测1~2次即可,全年监测频次分布更合理。监测项目分为必测项目和选测项目,必测项目为12~20项,选测项目为3~11项。     

Topographic Effects on Soil Organic Carbon in Louisiana Watersheds

Terrestrial carbon storage is influenced by a number of environmental factors, among which topographic and geomorphological features are of special significance. This study was designed to examine the relationships of soil organic carbon (SOC) density to various terrain parameters and watershed characteristics across Louisiana, USA. A polygon data set of 484 watersheds and 12 river drainage basins for Louisiana was used to form the landscape units. SOC densities were calculated for each soil map unit using the State Soil Geographic (STATSGO) database. Average drainage densities and average slopes at watershed and basin scales were quantified with the 1:24 K Digital Elevation Models (DEM) data, and the Louisiana hydrographic water features. Correlation and regression analyses were performed to determine relationships among drainage density, slope, elevation, and SOC. The study found an average watershed drainage density of 1.6 km/km² and an average watershed slope of 2.9 degrees in Louisiana. The results revealed that SOC density at both watershed and basin scales was closely related to drainage density, slope, and elevation. SOC density was positively correlated with watershed drainage density, but negatively correlated with watershed slope gradient and elevation. Regression models were developed for predicting SOC density at watershed and basin scales, obtaining regression coefficients (r ²) ranging from 0.43 to 0.83. The study showed that estimation of SOC at watershed and drainage basin scales combining DEM data can be a feasible approach to improve the understanding of the relationships among SOC, topographic, and geomorphological features.     

An alternative approach to reconstructing organic matter accumulation with contrasting watershed disturbance histories from lake sediments

A number of proxies, including carbon to nitrogen ratio (C:N) and stable isotopes (delta(13)C and delta(15)N), have been used to reconstruct organic matter (OM) profiles from lake sediments and these proxies individually or in combination cannot clearly discriminate different sources. Here we present an alternative approach to elucidate this problem from lake sediments as a function of watershed scale land use changes. Stable isotope signatures of defined OM sources from the study watersheds, Shawnigan Lake (SHL) and Elk Lake (ELL), were compared with sedimentary proxy records. Results from this study reveal that terrestrial inputs and catchment soil coinciding with the watershed disturbances histories probably contributed in recent trophic enrichment in SHL. In contrast, cultural eutrophication in ELL was partially a result of input from catchment soil (agricultural activities) with significant input from lake primary production as well. Results were consistent in both IsoSource (IsoSource version 1.2 is a Visual Basic program used for source separation, (http://www.epa.gov/wed/pages/models/isosource/isosource.htm) and discriminant analysis (statistical classification technique).     

Effect of spatial variability of storm on the optimal placement of best management practices (BMPs)

It is significant to design best management practices (BMPs) and determine the proper BMPs placement for the purpose that can not only satisfy the water quantity and water quality standard, but also lower the total cost of BMPs. The spatial rainfall variability can have much effect on its relative runoff and non-point source pollution (NPSP). Meantime, the optimal design and placement of BMPs would be different as well. The objective of this study was to discuss the relationship between the spatial variability of rainfall and the optimal BMPs placements. Three synthetic rainfall storms with varied spatial distributions, including uniform rainfall, downstream rainfall and upstream rainfall, were designed. WinVAST model was applied to predict runoff and NPSP. Additionally, detention pond and swale were selected for being structural BMPs. Scatter search was applied to find the optimal BMPs placement. The results show that mostly the total cost of BMPs is higher in downstream rainfall than in upstream rainfall or uniform rainfall. Moreover, the cost of detention pond is much higher than swale. Thus, even though detention pond has larger efficiency for lowering peak flow and pollutant exports, it is not always the determined set in each subbasin.