Modern monthly effective recharge maps for the conterminous U.S., 2003-2015

This data set includes 1 km resolution monthly timescale estimates of the effective recharge component of the water budget over the time period from October 2003 - December 2015. These estimates were developed as water budget residuals using previously published data sets for other water budget components: PRISM precipitation (Daly et al., 2008), SNODAS snow water equivalent (National Operational Hydrologic Remote Sensing Center, 2004), SSEBop-WB evapotranspiration (Reitz et al., 2017a), a map of groundwater-sourced irrigation (Reitz et al., 2017b), and monthly surface runoff maps (Reitz et al., 2019). The recharge data were estimated as the difference between water supply (precipitation plus snow melt plus irrigation) and the other water budget components (snow accumulation, surface runoff, and ET) for a given month. In locations / months where the SNODAS snow accumulation data indicated greater snow accumulation than PRISM precipitation for that month, the snow accumulation was capped to the precipitation value. The monthly recharge maps represent the implications of these water budget component estimates on resulting recharge rates, and are not accompanied by an evaluative and interpretive journal article or report, so ought to be taken as preliminary estimates. The authors plan to follow this work with further efforts that will result in updated versions of monthly recharge maps, and accompanying interpretive and evaluative work. The data set here includes two versions of the monthly recharge maps. The raw version (e.g., "2003_raw.zip") includes negative values where the water budget component estimates for ET, runoff, and snow accumulation exceeded the water supply from precipitation and snow melt. The positive version (e.g., "2003_positive.zip") replaces these negative values with zeros. The positive version is the one that should be used for application of these data sets, but the raw version can be useful as an indication of the quality of the water budget estimates in a given location. References: Daly, C., Halbleib, M., Smith, J.I., Gibson, W.P., Doggett, M.K., Taylor, G.H., Curtis, J. and Pasteris, P.P., 2008, Physiographically sensitive mapping of climatological temperature and precipitation across the conterminous United States, Int. J. Climatol., 28(15), 2031. National Operational Hydrologic Remote Sensing Center, 2004, Snow Data Assimilation System (SNODAS) Data Products at NSIDC, Version 1. Snow Water Equivalent. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center, https://doi.org/10.7265/N5TB14TC. Accessed June 2017. Reitz, Meredith, Senay, G.B., and Sanford, W.E., 2017a, Combined remote sensing and water-balance evapotranspiration estimates (SSEBop-WB) for the conterminous United States: U.S. Geological Survey data release, https://doi.org/10.5066/F7QC02FK. Reitz, Meredith, Sanford, W.E., Senay, G.B., and Cazenas, Jeffrey, 2017b, Annual estimates of recharge, quick-flow runoff, and ET for the contiguous US using empirical regression equations, 2000-2013: U.S. Geological Survey data release, https://doi.org/10.5066/F7PN93P0. Reitz, M., and Sanford, W.E., 2019, Monthly timescale quick-flow runoff maps for the conterminous U.S., 1895-2017: U.S. Geological Survey data release, https://doi.org/10.5066/P9Y1RP02.

本数据集包含2003年10月至2015年12月期间、分辨率为1千米的月尺度水量平衡有效补给项估算结果。此类估算值通过水量平衡残差法计算得到，所用的其他水量平衡组分数据均来自已发表数据集：包括PRISM降水数据（PRISM precipitation，Daly等，2008）、SNODAS雪水当量数据（SNODAS snow water equivalent，美国国家业务水文遥感中心，2004）、SSEBop-WB蒸散（ET）数据（SSEBop-WB evapotranspiration，Reitz等，2017a）、地下水灌溉源分布图（Reitz等，2017b）以及月尺度地表径流图（Reitz等，2019）。

补给量的计算方式为当月供水总量（降水+融雪+灌溉）与其余水量平衡组分（积雪量、地表径流与蒸散（ET））的差值。在部分区域与月份中，若SNODAS积雪量数据显示当月积雪量超过PRISM降水量，则将积雪量上限设为该月降水量值。

本次生成的月尺度补给量地图仅展示了上述水量平衡组分估算结果对应的补给速率，并未配套相应的评估与解读性期刊论文或报告，因此仅可视为初步估算结果。本数据集的作者计划后续开展进一步研究，更新月尺度补给量地图并配套相关解读与评估工作。

本数据集包含两类月尺度补给量地图版本。原始版本（例如"2003_raw.zip"）中包含负值区域，对应当月蒸散（ET）、径流与积雪量的估算值超过降水与融雪供水的情况；修正后版本（例如"2003_positive.zip"）将此类负值替换为0。修正后版本适用于该数据集的实际应用，而原始版本可用于评估特定区域水量平衡估算结果的质量。

参考文献：
1. Daly, C., Halbleib, M., Smith, J.I., Gibson, W.P., Doggett, M.K., Taylor, G.H., Curtis, J. and Pasteris, P.P., 2008, Physiographically sensitive mapping of climatological temperature and precipitation across the conterminous United States, Int. J. Climatol., 28(15), 2031. 译为：戴利（C. Daly）等，2008年，《美国本土地区气候学温度与降水的地貌敏感制图》，《国际气候学杂志》，第28卷第15期，第2031页。
2. National Operational Hydrologic Remote Sensing Center, 2004, Snow Data Assimilation System (SNODAS) Data Products at NSIDC, Version 1. Snow Water Equivalent. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center, https://doi.org/10.7265/N5TB14TC. Accessed June 2017. 译为：美国国家业务水文遥感中心，2004年，《美国国家冰雪数据中心（NSIDC）SNODAS数据产品第1版：雪水当量》，美国科罗拉多州博尔德：国家冰雪数据中心，https://doi.org/10.7265/N5TB14TC，2017年6月访问。
3. Reitz, Meredith, Senay, G.B., and Sanford, W.E., 2017a, Combined remote sensing and water-balance evapotranspiration estimates (SSEBop-WB) for the conterminous United States: U.S. Geological Survey data release, https://doi.org/10.5066/F7QC02FK. 译为：Reitz, M.、Senay, G.B.与Sanford, W.E.，2017a年，《美国本土地区结合遥感与水量平衡的蒸散（SSEBop-WB）估算》，美国地质调查局数据发布，https://doi.org/10.5066/F7QC02FK。
4. Reitz, Meredith, Sanford, W.E., Senay, G.B., and Cazenas, Jeffrey, 2017b, Annual estimates of recharge, quick-flow runoff, and ET for the contiguous US using empirical regression equations, 2000-2013: U.S. Geological Survey data release, https://doi.org/10.5066/F7PN93P0. 译为：Reitz, M.、Sanford, W.E.、Senay, G.B.与Cazenas, J.，2017b年，《2000-2013年美国本土地区基于经验回归方程的补给量、快速径流与蒸散（ET）年度估算》，美国地质调查局数据发布，https://doi.org/10.5066/F7PN93P0。
5. Reitz, M., and Sanford, W.E., 2019, Monthly timescale quick-flow runoff maps for the conterminous U.S., 1895-2017: U.S. Geological Survey data release, https://doi.org/10.5066/P9Y1RP02. 译为：Reitz, M.与Sanford, W.E.，2019年，《1895-2017年美国本土地区月尺度快速径流地图》，美国地质调查局数据发布，https://doi.org/10.5066/P9Y1RP02。