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Question: Does groundwater affect optimal population size?

Question: Does groundwater affect optimal population size?. Definitions:. groundwater services: conditions & processes through which groundwater provides benefits to human society. extractive groundwater services: drinking water irrigation industrial uses.

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Question: Does groundwater affect optimal population size?

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  1. Question:Does groundwater affect optimal population size?

  2. Definitions: groundwater services: conditions & processes through which groundwater provides benefits to human society • extractive groundwater services: • drinking water • irrigation • industrial uses • non-extractive groundwater services: • soil moisture for vadose zone • base flow for rivers & streams

  3. saprolite water table alluvium Fractured bedrock

  4. Question:How much groundwater is there?Answer: Lots! ** but it’s not evenly distributed & we need to leave most of it in the ground anyway to protect non-extractive groundwater services.

  5. sustainable groundwater management: non-extractive groundwater services receive primacy over extractive groundwater services

  6. or… (maximum sustainable extraction volume) equals (volume of groundwater supplied by recharge) minus (volume of groundwater required to support non-extractive services)

  7. How do we quantify non-extractive groundwater services? percentage of impervious land cover is a proxy for degradation of non-extractive groundwater services

  8. 5-20% impervious land cover, equivalent to 5-20% reduction in recharge,causes degradation of aquatic ecosystems due (in part) to decline in stream base flow…. 80-95% of groundwater recharge is needed to supply non-extractive groundwater services. 5-20% of groundwater recharge is available for extractive groundwater services under a sustainable groundwater management paradigm.

  9. a community’s sustainable population size is determined, in part, by availability of sustainably managed groundwater …not by availability of groundwater for unthrottled extraction

  10. quantitative example: 1000 acres, EBRF theoretical recharge available: 1.08 MGD under sustainable management, volume required for non-extractive services: 80-95% of recharge(.8 -1.02 MGD) theoretical maximum sustainable extraction: 5-20% of recharge (.05 – .2 MGD) theoretical sustainable maximum, entire EBRF: 3.9 – 7.8 MGD (25 – 49% of projected municipal demand at build out)

  11. policy recommendations: • adopt principles of sustainable groundwater management that couple allowable groundwater extraction volumes with protection of non-extractive groundwater services • protect groundwater recharge by limiting watershed impervious land cover & maximizing storm water infiltration • use community wells to serve rural residential development densities greater than 1 house per 2 acres • research recharge and groundwater flow relative to areas of high potential for sustainable extraction • usesustainably managed groundwater to augment municipal water supply in Charlottesville and Albemarle

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