Outside the Refuge in the region of hydrologic influence (RHI) the hydro_ln data was taken from the National Hydrography Dataset (NHD) Plus. The major streams were extracted from NHD Plus using a Strahler stream order greater than two and were clipped to the RHI, defined by a watershed delineation just downstream of the refuge using U.S. Geologic Survey's Streamstats online delineation tool. Inside refuge borders the Hydro_ln feature class is represented by digitized streams, ditches and canals. The digitization was done using National Agriculture Inventory Program's 2010 aerial imagery and a georectified image of an old irrigation map found in the basement at the refuge.
