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Soil-Water-Balance model developed to simulate net infiltration, irrigation water requirements, and other water budget components in support of the Central Sands Lakes Study, Wisconsin

February 14, 2022

This model archive provides input and output for Soil-Water-Balance (SWB) models developed for the Central Sands Lake study in central Wisconsin; this archive supplements the technical appendix in a report to the Wisconsin State Legislature written by the Wisconsin Department of Natural Resources (WDNR) in response to 2017 Wisconsin Act 10. This legislation directed DNR to determine whether existing and potential groundwater withdrawals are causing or are likely to cause significant reduction of mean seasonal water levels at Pleasant Lake, Long Lake, and Plainfield Lake (s. 281.34(7m)(2)(b), Wis. Stats.) in Waushara County, Wisconsin. The Soil-Water-Balance code (Westenbroek and others, 2018) partitions precipitation into rainfall and snowmelt, simulates the change in soil moisture within the root zone of crops and other vegetation, and estimates potential crop irrigation water requirements based on the needs of the vegetation. The amount of water escaping the root zone of plants (net infiltration or potential recharge) and the estimated crop water demand were fed into a related groundwater flow model in order to evaluate how landscape-level changes in crop type and irrigation requirements end up affecting groundwater and lake levels over time. The associated groundwater flow model is contained in a separate ScienceBase archive (https://doi.org/10.5066/P9SOJ01N). The period of 2012-2018 was used for parameter estimation (synonymously referred to as "history matching") for the groundwater models. This time period was chosen because it includes the most complete water use records to simulate groundwater withdrawals. The SWB2 model run for this period (called 'regional' under the directory that contains simulation scenarios, run at a resolution of 100m) was used to supply only net infiltration (potential recharge) values to the groundwater flow model. History matching was performed using groundwater elevations, lake stages, and streamflow observations over the 2012-2018 time period and processed observations derived from those raw data. A set of lower-resolution (200m) scenario runs were made to support the WDNR in their charge to evaluate the impact of water withdrawals on lake elevations. Three scenarios were created, driven by daily weather data as estimated by PRISM data (PRISM Climate Group, 2020) spanning the period 1981 to 2018. These scenarios, although based on real daily weather data, rely on three synthetic sets of input data and therefore should not be viewed as representing any specific time period. The scenarios represent: 1) 'current irrigation', in which land-use patterns and irrigation mask inputs are statistically generated based on the current frequency of crop rotations; 2) 'no irrigation, pre-development land-use', in which agricultural lands are converted to some non-irrigated agriculture or other non-agricultural land-use; 3) 'full development', where all lands with potential use for agricultural purposes (appropriate drainage and slope, for example) are converted to land-use and irrigation masks in a manner similar to scenario 1 development. The assumptions behind the scenario generation are detailed in Fienen and others (2021).