Coupling watershed modeling,public engagement,and soil analysis improves decision making for targeting P retention wetland locations

Constructed and restored wetlands can be effective sinks for particulate and dissolved phosphorus (P) if properly managed, but identifying suitable P retention wetland locations remains challenging. From a landscape perspective, Soil and Water Assessment Tool (SWAT) models identify locations within target watersheds with high nutrient loads that exhibit appropriate site characteristics and hydrodynamics. However, soil properties vary at the field scale, dictating the capacity of wetland systems to remove P and ultimately determining if a given wetland will operate as a sink or source of P over time. Land ownership and site access further complicate identification of P retention wetland locations. As a result, optimization and identification of P retention wetland locations requires analysis at both 1) watershed and 2) field scales, and 3) public engagement. In response, a survey effort linked SWAT model results that identified locations with target watersheds with field soil P storage capacity data and interested landowners. Results suggest that several locations recommended for their high SWAT-predicted P loading and landowner interest were in fact not well suited for project implementation due to soil P saturation and legacy P constraints. These findings highlight the need to couple watershed models with field scale soils analysis to identify locations for P retention wetlands in order to avoid unintended P release. Additionally, increased collaboration with social scientists and others familiar with public engagement strategies is needed to improve outreach activities targeting regional water quality improvements. Practical applications for nutrient retention wetland site selection are also discussed.     

Delineating spatial distribution and thickness of unconsolidated sand along the southwest Lake Michigan shoreline using TEM and ERT geophysical methods

Erosion and accretion of various magnitudes occur along the southwest Lake Michigan shoreline. These processes are triggered by natural events and human activities, which affect the distribution and thickness of sand on the nearshore lake bottom. Significant erosion along the Illinois coastline has highlighted the need for a large-scale means of acquiring spatially rich data to build models of sand distribution along the entire shoreline. Thus, we implemented a high-resolution airborne transient electromagnetic (TEM) method, coupled with a ground-based electrical resistivity tomography (ERT) method to determine the sand distribution and thickness along the shore from the beach to ~1 km into the lake. From Kenosha, Wisconsin, to Chicago, Illinois, we acquired 1049 line-km of TEM data, and 13.43 line-km of ERT data. Our results indicated a distinct, uneven distribution and thickness of the unconsolidated sand unit covering the southwestern Lake Michigan shoreline. The unconsolidated sand unit was found to range in thickness from 0 to ~12 m. This unconsolidated sand unit was shown to be thickest (4.5 to ~10 m) in the northern part of the study site. In southern Wisconsin and Chicago, the sand layer beneath the water column was found to be very thin, ≤1 m. We propose, based on our analysis, that lake-bed conditions and wind direction are the main factors that limit southward littoral transport. Our data suggest that the current state of the shoreline is relatively analogous to how it has always behaved; however, anthropogenic disturbance has exacerbated the natural patterns of erosion and accretion.     

太湖及太浦河两岸地区洪涝风险分析及对策探讨

由于特殊的自然地理条件,加之人类活动频繁,太湖及太浦河两岸地区的防洪、水资源和水环境等问题交织在一起,导致洪涝风险成因复杂,洪水风险长期存在。分析了该地区的洪涝风险特性,包括太湖水位易涨难消、太浦河两岸地区洪涝风险互相转化、上下游洪水风险转移,以及下垫面、引调水的变化而导致的洪水风险分布随之调整等;根据分析结果,对该地区的洪涝风险类型进行了识别。在此基础上,提出了科学精细调度水利工程、提升平原河网洪水风险分析技术、建立洪水风险实时分析系统以及探索"风险共担"的洪水管理模式等方面的建议。     

1980～2015年长江流域土地利用变化分析

基于长江流域1980,1990,1995,2000,2005,2010,2015年7期土地利用数据,通过土地利用转移矩阵以及多种指标,分析了1980~2015年间长江流域土地利用的时空变化过程。研究表明：近35 a来耕地和草地呈下降趋势,而林地、水域和城乡用地面积明显增加,未利用地总体呈下降趋势;随着时间的推移,各地类的变化形式由以交换变化量为主导转变为以净变化量为主导,说明各地类逐渐倾向于在原有空间位置发生面积变化,而不是在流域内发生空间位置转移;长江流域土地利用综合动态度从大到小排列依次是1990~1995年、1980~1990年、2005~2010年、1995~2000年、2000~2005年、2010~2015年。1980~1990年和1990~1995年这两个时期的综合土地利用综合动态度明显大于其他各时期,即这两个时期长江流域土地利用变化程度最为剧烈。     

CMADS驱动SWAT模型在水循环模拟中的应用——以洱海流域为例

基于大气数据驱动水文模型的输出结果开展水循环模拟研究是大气和水文学界的研究热点。利用中国大气同化驱动数据集CMADS驱动SWAT模型,模拟2009～2016年期间洱海流域关键水循环要素的时空分布特征。结果表明:①CMADS数据集可很好地驱动SWAT模型,在洱海流域适用性较好,可用于水循环模拟研究。②从时间上看,洱海流域年降水量、实际蒸散和年产水量均呈现出先减少后增加的趋势,分别以4.6,29.3,15.0 mm/a的速率递增,多年平均降水量、多年平均实际蒸散发和多年平均产水量分别为792.8,565.5,286.1 mm。从空间上看,洱海西部降水最丰沛,东部地区次之,北部地区最低;实际蒸散发空间差异性相对较小,高值区主要分布于洱海湖区周围;产水量空间分布差异性较大,洱海西部产水量最大,其次为洱海北部和东部山区。③湿润度呈现出增加的趋势,而产水系数表现出减少的趋势,多年平均湿润度和产水系数分别为0.61和0.43;实际蒸散发与降水变化趋势一致,但与潜在蒸散发变化趋势相反,表明水分条件是限制洱海流域潜热的主要因子。     

长江中游监利段近10年水位流量响应关系新特点

为了掌握三峡水库试验性蓄水以后长江监利河段水位流量响应关系新特点,以监利水文站为代表,采用数理统计、影响因素相关分析等方法进行了研究。结果表明:三峡水库蓄水后,尤其是试验性蓄水后监利河段河床冲刷,同水位过水面积增加,但监利站水位流量关系随断面冲淤调整的特征与下荆江裁弯及三峡水库蓄水初期河床冲刷引起的水位流量关系变化特征有较大不同。下荆江裁弯引起监利站各流量级相应水位降低0.62～0.95 m;蓄水初期(2003～2008年),监利站实测流量点群中心线同流量对应水位比蓄水前有所下降。试验性蓄水期(2009～2018年),同流量对应水位仅在枯水期有明显降低,随着流量级增加,水位降低幅度逐渐减小,当流量超过平滩流量,对应水位基本无变化。水面比降是监利段水位流量关系的主要影响因素,河床冲刷是次要影响因素;该河段水位流量特征的变化受洞庭湖出流顶托影响不明显。     

基于SWMM的铁心桥实验基地内涝防治效果模拟

基于南京水科院铁心桥实验基地的地形、下垫面条件等数据构建了SWMM,模拟了实验基地象目湖观景平台和水上餐厅两个监测点在不同降雨重现期、低影响开发措施、溢流孔设置和水泵强排条件下受淹情况。结果表明,初始水位较低(25.1 m)时,象目湖遭遇500年一遇的降雨事件时水位并未抬升至水上餐厅。初始水位较高(25.6 m)时,200年一遇和500年一遇的降雨事件中水上餐厅受淹持续时间分别为7 h和11 h。采用集水池、雨水花园和生物滞留池3种LID措施对象目湖水位峰值影响模拟结果显示,在5年或10年一遇的降雨事件中雨水花园和集水池可以分别降低象目湖峰值水位0.06 m和0.02 m,生物滞留池没有削减峰值水位。在降雨量为218.5 mm的20160707次降雨事件中LID措施削减象目湖水位效果不明显。水泵抽排流量越大,象目湖水位越早回落到观景平台以下。LID在应对造成城市内涝的低频次、短历时强降雨方面作用有限,铁心桥实验基地象目湖内涝防治应以加强水文气象预测和水位管理、加大溢流孔尺寸和采用水泵强排等措施为主。     

奎屯河流域健康评价

以新疆典型的干旱内陆河流域--奎屯河流域为研究对象,在确定流域健康评价时空尺度的基础上,提出涵盖流域水资源健康、涉水生态环境健康、社会经济健康的评价指标体系,构建基于组合赋权与协调发展度的流域健康评价模型。结果表明:现状年(2015年)处于亚健康状态的分区有:子区1、子区2、子区3、子区6,综合评价指数分别为:0.419、0.404、0.408、0.401,协调发展类型为临界协调发展;处于不健康状态的分区有:子区4和子区5,综合评价指数为0.358和0.343,协调发展类型属于中度不协调衰退型。     

博斯腾湖流域水资源管理决策支持系统设计与实现

为了提高博斯腾湖流域水资源管理水平,设计开发了针对该流域的水资源管理决策支持系统。系统基于Microsoft.NET平台,采用Visual Studio、SQL Server、ArcGIS工具集开发,在流域“地-云-空”一体化监测体系和系统架构的基础上,构建了地图要素管理、基本水文信息、流域生态流量等主要模块,实现了流域空间可视化查询、实时流量动态模拟、流域生态基流计算以及水资源管理配置等功能。结合博斯腾湖流域1956—2019年水文资料及目前数据获取情况,系统可为不同发展模式下水资源管理提供多方面参考信息和技术支撑,能有效提高水资源管理部门决策效率。     

Temporal and spatial dynamics of surface run‐off from Lake Basaka catchment (Ethiopia) using SCS‐CN model coupled with remote sensing and GIS

The Lake Basaka catchment (Ethiopia) has undergone a significant land use–land cover (LULC) change and lake level rise over the past five decades. Significant quantities of water and sediment flow annually into the lake through erosion processes. An appropriate method of estimating the surface run‐off from such ungauged and dynamic catchment is extremely important for delineating sensitive areas (based on run‐off responses) to be protected and for development of suitable measures to reduce run‐off and associated soil loss. Reliable prediction of run‐off, however, is very difficult and time‐consuming for catchments such as that of Lake Basaka. The present study estimated the dynamics of surface (direct) run‐off using the NRCS‐CN model in ArcGIS, assisted by remote sensing and ancillary data. The results indicated the Lake Basaka catchment experienced significant temporal and spatial variability in its run‐off responses, depending on the rainfall (amount and distribution) pattern and LULC changes. A significant run‐off increase occurred after 1973, consistent with significant LULC changes and lake level increments occurring after that period. A reduced vegetation cover also resulted in increased run‐off coefficient of the lake catchment from 0.11 in the 1970s to 0.23 in the 2000s, indicating the important need to consider possible future LULC evolution when forecasting the lake catchment run‐off behaviour.