GroMoPo Metadata for Sprague River Watershed SWAT-MODFLOW model

Interaction between groundwater and surface water in watersheds has significant impacts on water management and water rights, nutrient loading from aquifers to streams, and in-stream flow requirements for aquatic species. Of particular importance are the spatial patterns of these interactions. This study explores the spatio-temporal patterns of groundwater discharge to a river system in a semi-arid region, with methods applied to the Sprague River Watershed (4100km(2)) within the Upper Klamath Basin in Oregon, USA. Patterns of groundwater-surface water interaction are explored throughout the watershed during the 1970-2003 time period using a coupled SWAT-MODFLOW model tested against streamflow, groundwater level and field-estimated reach-specific groundwater discharge rates. Daily time steps and coupling are used, with groundwater discharge rates calculated for each model computational point along the stream. Model results also are averaged by month and by year to determine seasonal and decadal trends in groundwater discharge rates. Results show high spatial variability in groundwater discharge, with several locations showing no groundwater/surface water interaction. Average annual groundwater discharge is 20.5m(3)/s, with maximum and minimum rates occurring in September-October and March-April, respectively. Annual average rates increase by approximately 0.02m(3)/s per year over the 34-year period, negligible compared with the average annual rate, although 70% of the stream network experiences an increase in groundwater discharge rate between 1970 and 2003. Results can assist with water management, identifying potential locations of heavy nutrient mass loading from the aquifer to streams and ecological assessment and planning focused on locations of high groundwater discharge. Copyright (c) 2016 John Wiley & Sons, Ltd.

流域内地下水与地表水的交互作用，对水资源管理、水权界定、含水层向溪流的养分输移，以及满足水生生物需求的河道内流量要求均具有显著影响，其中此类交互作用的空间分布格局尤为关键。本研究针对半干旱区域某水系的地下水排泄时空分布特征展开探究，研究区域选定为美国俄勒冈州上克拉马斯盆地内的斯普拉格河流域（面积4100平方千米）。研究以1970-2003年为时间跨度，采用SWAT-MODFLOW耦合模型对全流域的地下水-地表水交互模式进行分析；该模型已通过溪流流量、地下水位以及野外估算的河段特异性地下水排泄速率完成验证。模型采用日时间步长与耦合机制，针对溪流沿线的每个模型计算单元计算地下水排泄速率；同时对模型结果按月、按年进行平均，以揭示地下水排泄速率的季节与年代际变化趋势。研究结果显示，地下水排泄存在高度的空间异质性，部分区域未出现地下水与地表水的交互作用。流域年均地下水排泄总量为20.5立方米每秒，排泄速率的峰值与谷值分别出现在9-10月与3-4月。在1970至2003年的34年间，年均排泄速率以约0.02立方米每秒·年的速率逐年递增，该增幅相较于年均排泄速率而言微乎其微；但全流域70%的溪流网络的地下水排泄速率均呈上升趋势。本研究结果可辅助水资源管理工作，识别含水层向溪流输送高养分负荷的潜在区域，同时为聚焦于高地下水排泄区域的生态评估与规划提供决策支持。版权所有©2016 约翰·威利父子出版有限公司（John Wiley & Sons, Ltd.）