Assessing Watershed-Scale, Long-Term Hydrologic Impacts of Land-Use Change Using a GIS-NPS Model

Land-use change, dominated by an increase in urban/impervious areas, has a significant impact on water resources. This includes impacts on nonpoint source (NPS) pollution, which is the leading cause of degraded water quality in the United States. Traditional hydrologic models focus on estimating peak discharges and NPS pollution from high-magnitude, episodic storms and successfully address short-term, local-scale surface water management issues. However, runoff from small, low-frequency storms dominates long-term hydrologic impacts, and existing hydrologic models are usually of limited use in assessing the long-term impacts of land-use change. A long-term hydrologic impact assessment (L-THIA) model has been developed using the curve number (CN) method. Long-term climatic records are used in combination with soils and land-use information to calculate average annual runoff and NPS pollution at a watershed scale. The model is linked to a geographic information system (GIS) for convenient generation and management of model input and output data, and advanced visualization of model results. The L-THIA/NPS GIS model was applied to the Little Eagle Creek (LEC) watershed near Indianapolis, Indiana, USA. Historical land-use scenarios for 1973, 1984, and 1991 were analyzed to track land-use change in the watershed and to assess impacts on annual average runoff and NPS pollution from the watershed and its five subbasins. For the entire watershed between 1973 and 1991, an 18% increase in urban or impervious areas resulted in an estimated 80% increase in annual average runoff volume and estimated increases of more than 50% in annual average loads for lead, copper, and zinc. Estimated nutrient (nitrogen and phosphorus) loads decreased by 15% mainly because of loss of agricultural areas. The L-THIA/NPS GIS model is a powerful tool for identifying environmentally sensitive areas in terms of NPS pollution potential and for evaluating alternative land use scenarios for NPS pollution management.     

Allocation of supplementary aeration stations in the Chicago waterway system for dissolved oxygen improvement

The Chicago Waterway System (CWS), used mainly for commercial and recreational navigation and for urban drainage, is a 122.8 km branching network of navigable waterways controlled by hydraulic structures. The CWS receives pollutant loads from 3 of the largest wastewater treatment plants in the world, nearly 240 gravity Combined Sewer Overflows (CSO), 3 CSO pumping stations, direct diversions from Lake Michigan, and eleven tributary streams or drainage areas. Even though treatment plant effluent concentrations meet the applicable standards and most reaches of the CWS meet the applicable water quality standards, Dissolved Oxygen (DO) standards are not met in the CWS during some periods. A Use Attainability Analysis was initiated to evaluate what water quality standards can be achieved in the CWS. The UAA team identified several DO improvement alternatives including new supplementary aeration stations. Because of the dynamic nature of the CWS, the DUFLOW model that is capable of simulating hydraulics and water quality processes under unsteady-flow conditions was used to evaluate the effectiveness of new supplementary aeration stations. This paper details the use of the DUFLOW model to size and locate supplementary aeration stations. In order to determine the size and location of supplemental aeration stations, 90% compliance with a 5 mg/l DO standard was used as a planning target. The simulations showed that a total of four new supplementary aeration stations with oxygen supply capacities ranging from 30 to 80 g/s would be sufficient to meet the proposed target DO concentration for the North Branch and South Branch of the Chicago River. There are several aeration technologies, two of which are already being used in the CWS, available and the UAA team determined that the total capital costs of the alternatives range from $35.5 to $89.9 million with annual operations and maintenance costs ranging from $554,000 to $2.14 million. Supplemental aeration stations have been shown to be a potentially effective means to improve DO concentrations in the CWS and will be included in developing an integrated strategy for improving water quality in the CWS.     

Integrated environmental management: strengthening the conceptualization

Although espoused by many, integrated environmental management (IEM) has been difficult to accomplish in practice. There are many reasons for this shortfall, but certainly a key factor is the lack of agreement among scholars and practitioners regarding the concept and its defining elements. Our purpose here is to sharpen the conceptual basis for IEM by elaborating and pragmatically characterizing a framework for the practice of more integrated environmental management. We outline four fundamental dimensions of IEM: (1) comprehensive, (2) interconnective, (3) strategic, and (4) interactive/coordinative. IEM efforts in the Black Earth Creek watershed in Wisconsin illustrate specific attributes and examples pertaining to our conceptualization of IEM. Acceptance of the conceptual framework elaborated here should alleviate some of the confusion associated with IEM and help move this widely heralded approach from theory into practice.     

黄河中游砒砂岩地区长川流域土壤侵蚀情景分析

根据已有研究成果和相关资料,采用情景分析(scenario analysis)法,评价黄河中游砒砂岩地区长川流域实施不同水土保持和退耕还林(草)措施对土壤侵蚀的影响.结果表明:水土保持生物措施和工程措施减少土壤侵蚀的效益显著,相对而言,退耕还林(草)对流域总体土壤侵蚀影响不大.水土保持和退耕还林(草)的组合情景方案对土壤侵蚀影响较大,部分组合情景的土壤侵蚀甚至可低于土壤侵蚀背景值.可见,水土保持措施结合退耕还林(草)可以控制和减少研究区土壤侵蚀.在今后水土流失综合治理过程中,应首推生物和工程措施辅以退耕还林(草)措施.     

Input- and output-oriented approaches to implementing ecosystem management

Input- and output-oriented approaches to landscape management have distinct roles for resource protection, environmental restoration, and sustainable land management. Implementing recent proposals for ecosystem management in the western United States involves a synthesis of input and output management. Within the broader context of ecosystem management, input management focuses on tailoring land use to the landscape, whereas output management employs assessments of resource condition to trigger modified management activity once resources are degraded to specified threshold conditions. Current approaches to landscape-scale management, however, tend to rely primarily on output-oriented strategies that are most effective for monitoring environmental conditions. Current uses of input management focus on environmental impact assessments, which generally are site- or project-specific analyses. The compeexity and dynamic nature of ecosystems, and the range of scales over which ecological processes operate, imply that development and incorporation of input-oriented approaches into landscape-scale management is necessary to implement ecosystem management as a strategy for sustainable land use.     

绿洲浅层地下水位与水质变化对人为驱动LUCC的响应——以三工河流域为例

以新疆三工河流域绿洲为例,应用遥感、地理信息系统、空间插值和统计分析的方法,初步分析干旱区绿洲土地利用/土地覆被变化对绿洲浅层地下水位水质变化的影响。研究数据包括1978、1987和1998年三期遥感数据和近25年8口常年观测井水位数据及1987和1998年两期20口观测井水质数据。结果表明,绿洲随着城市、工矿用地为主的非农业用地和以耕地为主的农业用地的持续增加,浅层地下水水位与水质发生了显著性的时空变化。冲洪积扇绿洲主要城镇聚居区地下水位以年均45cm的速率下降,冲积平原下部绿洲地下水位以年均7cm的速率呈现缓慢的上升趋势;绿洲地下水水质趋于恶化,矿化度总体呈现上升的态势,且冲积平原绿洲地下水矿化度上升的幅度普遍大于冲洪积扇绿洲,这与地形、水文地质条件、土地资源开发、灌排强度、地表蒸发、化学肥料和农药的使用密切相关。     

Climate change and sandy land development in Qinghai Lake Watershed, China

The Qinghai Lake Watershed, containing the largest saline lake in northwest of China, has suffered from severe sandy land development in recent years. This paper analyzes its daily precipitation, temperature, and wind from 1958 to 2001, and the spatial and temporal distributions of sandy land through the interpretation of remote sensing images covering four years (1977, 1987, 2000, and 2004). Results showed that since the middle of the 1960s, the daily precipitation (P) of 0<P⩽5 mm decreased, while the P>20 mm increased significantly (S<0.05) in their annual total amounts and days. The maximum daily precipitation also increased significantly. Both the maximum dry spell and the total dry spell of more than ten days had a significant upward trend. Since the beginning of the 1960s, all the extremely high, extremely low and mean temperatures increased significantly (S<0.01), at a rate of 0.1°C/10a, 0.2°C/10a, and 0.2°C/10a, respectively. The days with extremely high temperature had a significant upward trend, while the days with extremely low temperature had a significant downward trend. The Qinghai Lake was significantly shrinking (S<0.01) and provided abundant sediments for Aeolian erosion. The NNW wind prevailed in the watershed, and the largest scale wind was from the west and concentrated on the dry months. As a result, the sandy land was mainly born on the east bank of Qinghai Lake. The total sandy land area in the watershed had grown from 587.4 km², 660.7 km², 697.6 km² to 805.8 km², accordingly, its area percentage growing from 2.0%, 2.2%, 2.4% to 2.7%, respectively.     

香溪河流域人类活动净磷输入量及其影响因素

为了阐明三峡库区第一大支流香溪河流域人类活动对磷输入的影响程度,收集流域所涉及的2001~2019年的乡镇统计数据,运用改进的人类活动净磷输入（NAPI）模型,分析了该流域NAPI的发展趋势.结果表明：在时间尺度上,香溪河流域2001~2019年的NAPI整体呈下降趋势;在空间尺度上,NAPI呈现东北部高于西南部的趋势,影响香溪河流域NAPI的主要乡镇为黄粮镇、峡口镇和昭君镇,占香溪河流域NAPI的63.8%;河流磷输出占NAPI的百分比为10.7%~79.5%;从NAPI结构上看,影响香溪河流域NAPI主要的影响因素为磷肥施入量,占香溪河流域NAPI的46%~68%,次要影响因素为食物磷和磷化工及磷矿开采导致磷素释放量,分别占香溪河流域NAPI的14%~32%和16%~24%;从NAPI影响因素上看,NAPI与人口密度和耕地面积占比均呈极显著正相关（P<0.001）,而在小流域研究尺度上,NAPI与河流磷输出的相关性不显著（P>0.05）,不具有直接的响应关系.因此,香溪河流域磷素管理应优先考虑重点区域（黄粮镇、峡口镇和昭君镇）,控制化肥施用量,并提高工厂污染物排放标准.     

基于地理探测器的流域土壤磷流失影响因素分析

基于修正的通用土壤流失方程(RUSLE)和地理探测器,定量分析了甘肃白龙江流域土壤磷流失的空间分异及其影响因素.结果表明:①2014年流域平均土壤磷流失量为0.214 t·km~(-2)·a~(-1),流失总量为3945.38 t·a~(-1);②磷流失空间分布较为破碎,热点区集中于迭部北部和舟曲东北部等高山区及舟曲、文县和武都三区县交界的低山河谷区,冷点区集聚于宕昌北部耕作区和文县南部森林保护区;③流域磷流失的空间分异主要受土地利用和地形的影响,农牧业生产也发挥了一定作用,磷流失整体表现为随海拔和坡度的抬升而增加,草地林地耕地;④流域及其内部冷热区影响因素差异较大,这是由各区地理环境协同差异所致,最大交互因子分别为土壤类型∩景观破碎度、土壤类型∩植被覆盖度、降水∩第一产业从业人口比重.在流域磷流失治理中,应合理安排农牧业生产,在提高植被覆盖度的同时降低景观破碎度.