Drought Conditions Indicators for Delaware

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Water is one of the most important natural resources on earth and is especially true for the State of Delaware. It is essential for meeting the needs of all segments of our society and for maintaining economic growth and agriculture. At this time, south of the Chesapeake and Delaware Canal, all water used for public and domestic supply and more than 98% of water used for irrigation is groundwater. North of the canal, approximately 70% of public water supplies are obtained from surface-water sources (streams and creeks) and 30% from groundwater resources. Delaware is susceptible to both short-term and long-term drought conditions, which are specifically highlighted in Delaware’s State Hazard Mitigation Plan and rank high in natural hazard vulnerability in each county. Significant extended periods of dry conditions, as well as formal droughts, occurred during the mid-1960s, 1980s, and 1995 – 2002. Recent years have also seen a significant increase in temperatures in Delaware. The eight hottest years on record (since 1895) have all occurred since 1990, with 2012 ranking as the hottest (Source: NOAA Climate a a Glance, http://www.ncdc.noaa.gov/cag/)

The Delaware Geological Survey is significantly involved in numerous hydrologic data collection and monitoring activities, including the USGS stream and tide gaging programs, Delaware groundwater monitoring network, and a lead membership in the Delaware Water Supply Coordinating Council (WSCC). The WSCC, comprised of DGS, DNREC, UD Water Resources Agency, water purveyors, and personnel from each county, is tasked with providing technical guidance for a move up to or down from Drought Watch for Delaware. (The responsibility for a move up to or down from Drought Warning or Drought Emergency for Delaware lies with the Governor’s Drought Advisory Committee, with guidance from the WSCC.) WSCC reviews numerous types of information when determining the severity of dry conditions, such as precipitation, stream flow, groundwater, reservoir levels, time of year, and water supply, among other factors. One of the primary numerical indicators used by the WSCC, the Water Conditions Index (WCI) for Northern New Castle County was developed by DGS in the 1980s at a time when data availability was limited and is not applicable for most of the state.

With proliferation of environmental observing systems throughout Delaware and the string of historically high summer temperatures during the last decade, the Water Supply Coordinating Council has expressed interest in re-evaluating the WCI and other established indices used in northern New Castle County as well as in establishing criteria and developing numerical indicators for both Kent and Sussex Counties as well. The current project will focus efforts to research past performance of the WCI for Northern New Castle County as compared with other established drought indicators and investigate modifying the WCI, if needed. We will also investigate the feasibility of quantifying water conditions in Kent and Sussex Counties by analyzing factors that are most important to these regions (i.e., precipitation, groundwater for agricultural irrigation, etc….) This project aims to improve the quality and extend the capabilities of the early warning system of drought in Delaware.

This project is a collaboration among the DGS, Office of Delaware State Climatologist, Delaware Environmental Observing System (DEOS), and Delaware Environmental Monitoring and Analysis Center (DEMAC).