How vulnerable is the groundwater here?

For the households on private wells, three things from the Ohio Geological Survey: the DRASTIC groundwater vulnerability index of the ground under the ZIP's population center (a 23 to 230 scale built from depth to water, recharge, aquifer, soil, slope, vadose zone and conductivity; higher means contamination from the surface reaches the aquifer more easily, and sand-and-gravel valleys with shallow water score highest), the karst features (sinkholes, springs and closed depressions) the survey has mapped inside the ZIP, where surface water can reach the aquifer in hours, and the state's inventory of water well logs, every well a driller has reported since the 1940s, counted inside the ZIP with median depth, yield and the split between bedrock and sand-and-gravel wells. Vulnerability describes the setting, not measured contamination. The nearest monitoring well adds the measured water table: the latest depth, the 2015 to 2019 average and whether it is running lower or higher. Urban Setting Designation areas, where Ohio EPA has agreed groundwater is not used for drinking, are flagged. Ohio EPA's Class V injection wells inside the ZIP are counted by type. Ohio EPA's wellhead protection areas and sensitive geologic settings, with ODNR's verified sinkholes and springs, say how exposed the aquifer is. A last row names Ohio EPA's nearest ambient groundwater monitoring well, its depth, rock and sampling schedule. A Nitrate risk row gives EPA researchers' modelled chance that a public system in the subwatershed exceeds the nitrate standard, for groundwater and surface-water supplies.

1,229 of 1,233 ZIPs have data; median 113 index.

Legend

Map of Ohio by Groundwater

Source

ODNR Division of Geological Survey: DRASTIC groundwater vulnerability polygon at each ZIP's population center, mapped karst features, and the state water well log inventory (about 655,000 logs) counted inside each ZIP; ODNR glacial, bedrock and sole source aquifer maps (Ohio EPA hydro/Aquifers) at the population center; groundwater levels at the nearest active monitoring well from the USGS Water Data OGC API (ODNR and USGS observation wells, depth to water since 2015); Ohio EPA Urban Setting Designation areas; Ohio EPA Class V underground injection control wells by ZIP; Ohio EPA source water protection areas and inner management zones for public wells (DrinkingWater/SWAP), karst and spring points and sensitive geologic settings (geology/Geology); Ohio EPA DrinkingWater/Ambient_GW_Monitoring well locations and construction (392 active wells), nearest to the ZIP center; EPA EnviroAtlas nitrate violation index (modelled probability of a public-system nitrate violation) for the subwatershed

ODNR Geological Survey · Ohio EPA GIS services · USGS water data

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