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Distributed Watershed Modeling of Design Storms to Identify Nonpoint Source Loading Areas
Author(s) -
Endreny T. A.,
Wood E. F.
Publication year - 1999
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1999.00472425002800020004x
Subject(s) - surface runoff , watershed , environmental science , hydrology (agriculture) , runoff curve number , nonpoint source pollution , runoff model , storm , time of concentration , water quality , ecology , geography , geology , meteorology , geotechnical engineering , machine learning , computer science , biology
Watershed areas that generate nonpoint source (NPS) polluted runoff need to be identified prior to the design of basin‐wide water quality projects. Current watershed‐scale NPS models lack a variable source area (VSA) hydrology routine, and are therefore unable identify spatially dynamic runoff zones. The TOPLATS model used a watertable‐driven VSA hydrology routine to identify runoff zones in a 17.5 km 2 agricultural watershed in central Oklahoma. Runoff areas were identified in a static modeling framework as a function of prestorm watertable depth and also in a dynamic modeling framework by simulating basin response to 2, 10, and 25 yr return period 6 h design storms. Variable source area expansion occurred throughout the duration of each 6 h storm and total runoff area increased with design storm intensity. Basin‐average runoff rates of 1 mm h −1 provided little insight into runoff extremes while the spatially distributed analysis identified saturation excess zones with runoff rates equaling effective precipitation. The intersection of agricultural landcover areas with these saturation excess runoff zones targeted the priority potential NPS runoff zones that should be validated with field visits. These intersected areas, labeled as potential NPS runoff zones, were mapped within the watershed to demonstrate spatial analysis options available in TOPLATS for managing complex distributions of watershed runoff. TOPLATS concepts in spatial saturation excess runoff modeling should be incorporated into NPS management models.