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Test of APEX for Nine Forested Watersheds in East Texas
Author(s) -
Wang X.,
Saleh A.,
McBroom M. W.,
Williams J. R.,
Yin L.
Publication year - 2007
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/jeq2006.0087
Subject(s) - environmental science , hydrology (agriculture) , watershed , hexazinone , water quality , sediment , surface runoff , streams , geology , ecology , weed control , paleontology , computer network , geotechnical engineering , machine learning , computer science , biology
Hydrologic/water quality models are increasingly used to explore management and policy alternatives for managing water quality and quantity from intensive silvicultural practices with best management practices (BMPs) in forested watersheds due to the limited number of and cost of conducting watershed monitoring. The Agricultural Policy/Environmental eXtender (APEX) model was field‐tested using 6 yr of data for flow, sediment, nutrient, and herbicide losses collected from nine small (2.58 to 2.74 ha) forested watersheds located in southwest Cherokee County in East Texas. Simulated annual average stream flow for each of the nine watersheds was within ± 7% of the corresponding observed values; simulated annual average sediment losses were within ± 8% of measured values for eight out of nine watersheds. Nash‐Sutcliffe efficiency (EF) values ranged from 0.68 to 0.94 based on annual stream flow comparison and from 0.60 to 0.99 based on annual sediment comparison. Similar to what was observed, simulated flow, sediment, organic N, and P were significantly increased on clear‐cut watersheds compared with the control watersheds. APEX reasonably simulated herbicide losses, with an EF of 0.73 and R 2 of 0.74 for imazapyr, and EF of 0.65 and R 2 of 0.68 for hexazinone based on annual values. Overall, the results show that APEX was able to predict the effects of silvicultural practices with BMPs on water quantity and quality and that the model is a useful tool for simulating a variety of responses to forest conditions.