Inventory of Interbasin Transfers in the United States

Interbasin transfers ( IBT s) are man‐made transfers of water that cross basin boundaries. These transfers are used to distribute water resources according to supply and demand. The objectives of this work were to quantify the number of IBT s that exist in the United States (U.S.) and to examine the distribution of IBT s and potential causes associated with any observed clustering of IBT s. Defining “basin” was important to enable determination of which transfers qualify as “interbasin.” A variety of definitions are employed by states, with no federal definition. The most recent national studies of IBT s were conducted by the U.S. Geological Survey (USGS) in 1985 and 1986 using USGS Hydrologic Unit Code ( HUC ) definitions of basins. To build a 2016 inventory of IBT s in the U.S., and to identify where they most commonly occur, the USGS National Hydrography Database ( NHD ) was utilized in conjunction with the Watershed Boundary Dataset ( WBD ). Transfers across HUC 6 basin boundaries were considered interbasin. Geographical information analysis with the NHD and WBD databases revealed that there are a total of 2,161 man‐made waterways crossing HUC 6 basin boundaries in the U.S. IBT s are somewhat concentrated: Florida, Texas, and North Carolina account for over 50% of the total identified IBT s. For some states, identified IBT s are locally clustered. Analysis of these clusters suggests a variety of reasons that IBT s have been built, including population, drainage, and agricultural factors.