DOI: 10.5066/p9fdly8p
title: Estimated monthly water use for irrigation by 12-digit hydrologic unit in the conterminous United States for 2015

description: This data release contains the output of the Irrigation Water Use Estimation Disaggregation and Downscaling Model (IWUEDD) along with the scripts and data resources (IWUEDD_basic.zip) required to replicate the output results. The IWUEDD is used to estimate monthly irrigation withdrawals and consumptive use for each 12-digit hydrologic unit code (HUC 12) subwatershed in the conterminous United States. The HUC 12-level estimates are separated into groundwater (GW), surface water (SW), groundwater and surface water combined (TW), and consumptive use (CU). The IWUEDD developed monthly estimates by disaggregating and downscaling previously published annual county-level irrigation withdrawal and consumptive use data complied as part of the National Water Use Science Project, National Water Census as presented in U.S. Geological Survey data release, "Estimated use of water in the United States county-level data for 2015" (Dieter and others, 2018). Method The IWUEDD is tested and developed with the Python Programing Language version 3.6.10 (python) using ESRI ArcGIS Pro 2.6.1 advanced license with spatial analysis extension enabled. The IWUEDD downscales reported annual county withdrawals to monthly withdrawals for each HUC 12. The IWUEDD uses preprocessed publicly available spatial and tabular data from county-level withdrawals (Dieter and others, 2018), county-level actual evapotranspiration (ETa) (Painter and others, 2021), field-level irrigated lands (Xie and Lark, 2021), regional climate zones (Godfrey, 1999), county boundaries (U.S. Census Bureau, 2015a), and hydrologic unit code (HUC) boundaries (U.S. Geological Survey, 2020). The data preprocessing for the IWUEDD is described in the UserGuide_IWUEDD_advanced.pdf in the supplemental materials folder (IWUEDD_advanced.zip). To estimate the monthly irrigation withdrawals, the IWUEDD: generates an area weighted estimated monthly withdrawal for each county based on the intersection of each hydrologic unit with climate zone and the ETa for that zone, spatially disaggregates the county-level irrigated withdrawals to HUC-level irrigated withdrawals using an area percentage based on the area of irrigated lands within a county-HUC producing monthly county-HUC withdrawal values, and sums monthly county-HUC values by HUC 12 resulting in a table of HUC 12-level monthly withdrawals. The IWUEDD has a few assumptions to note. The IWUEDD assumes that the irrigated lands dataset represents all irrigated land and that the withdrawals are only for crop irrigation. However, not all irrigated lands are accounted for by the Landsat-based Irrigation Dataset (LANID), produced by Xie and Lark (2021) of the University of Wisconsin and not all withdrawals were only for crop irrigation; some areas include golf coures irrigation with crop irrigation. As such to account for land not included in the LANID and withdrawals used for golf course irrigation a step was included in the IWUEDD to select counties that had a total withdrawal value in the original county-level data from Dieter and others (2018) but had a NULL total withdrawal value in the monthly irrigation withdrawals by HUC 12 tables (Read and others, 2021). Those counties are represented in the shapefile IWUEDD_Excluded_Counties.zip provided in this data release. No formal analysis was included for the non-crop withdrawals that are from golf course irrigation. Instead, observations made about the distribution of golf course irrigation were used to evaluate the non-crop withdrawals. It was observed that for counties with combined (crop and golf course) withdrawals the county either had a small number of golf courses and large area of irrigated land (withdrawals were mostly for crop irrigation) or a large number of golf courses and small area of irrigated land (withdrawals were negligible for crop irrigation). These observations showed that limited golf course withdrawals would be attributed to irrigated lands. To replicate the monthly irrigation withdrawals by HUC 12 tables in the data release (Read and others, 2021) download IWUEDD_basic.zip and follow the user guide. To adapt the IWUEDD for your own use download the IWUEDD_advanced.zip. The user is advised to read the user guide in IWUEDD_basic.zip or IWUEDD_advanced.zip for additional details about the functioning of the IWUEDD. The user is also advised that each data source used to generate this data release has independent metadata that should be reviewed as needed for additional information. User is advised to read: Filename "ReadMe_10.5066-P9FDLY8P.pdf" for method. Filename "UserGuide_IWUEDD_basic.pdf" for basic use. Filename "UserGuide_IWUEDD_advanced.pdf" for advanced use. Filename "Est_monthly_WU_for_IR_by_12-digit_HU_in_CONUS_for_2015.xml" for additional details