Urban Water Management Plan 2015

2015 City of Morgan Hill 7.0 CHAPTER 7 – WATER SUPPLY RELIABILITY ASSESSMENT Water supply reliability addresses the capability of the water supply during emergency events in normal existing conditions, single dry years and multiple dry years. The reliability also must be projected out for 20 years. 7.1 CONSTRAINTS ON WATER SOURCES Law 10631 (c)(2) For any water source that may not be available at a consistent level of use, given specific legal, environmental, water quality, or climatic factors, describe plans to supplement or replace that source with alternative sources or water demand management measures, to the extent practicable. 10634 The plan shall include information, to the extent practicable, relating to the quality of 7.1.1 Legal Factors The City’s sole source of supply is groundwater extracted from the Llagas subbasin of the Gilroy- Hollister Groundwater Basin and the Coyote Valley subarea of the Santa Clara subbasin, which is a part of the Santa Clara Valley Groundwater Basin. These groundwater basins and subbasins are not adjudicated basins and no legal factors are expected to limit the availability of supply. 7.1.2 Environmental Factors Environmental concerns can arise during the water planning process when a project’s impact on the ecosystem is taken into a consideration. These concerns can subsequently cause a lack of supply due to the enforcement of environmental legislation. The City’s groundwater sources are not expected to be limited by any environmental factors. 7.1.3 Water Quality Factors Water quality factors that could affect the availability of supply include water contamination due to biological or chemical constituents. The primary water quality factors that could potentially impact the City are related to perchlorate, nitrate, and hexavalent chromium contamination. In order to estimate the potential impact on supply due to water quality contamination, the production capacity of the largest capacity well is assumed to no longer be available to the City. This would result in a supply capacity reduction of approximately 2,400 afy. existing sources of water available to the supplier over the same five-year increments as described in subdivision (a) of Section 10631, and the manner in which water quality affects water management strategies and supply reliability.

August 2016

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City of Morgan Hill 2015 Urban Water Management Plan