Water-Supply Monitoring & Indicators NJ Water Supply Advisory Council October 2, 2015 Jeffrey L. Hoffman NJDEP - NJGWS
What is a Drought? There are 4 different types of droughts.
1. Meterological Drought Precipitation is less than normal for longer than normal.
2. Hydrologic Drought Reservoirs, streamflows & groundwater levels are lower than normal for longer than normal. Concerns about ecological impacts.
3. Agricultural Drought evapotranspiration > precipitation at a time when plants need water.
4. Water-Supply Droughts (Socioeconomic) “… a water supply shortage of a dimension which endangers the public health, safety, or welfare in all or any part of the State… N.J.S.A. 58:1A-4.a. NJDEP’s Drought of Concern
6 Regions Water-supply droughts may not affect all of NJ in same way. NJ divided into regions based on similar water-supply. Evaluate conditions in each region. Use municipal boundaries to help local officials apply water restrictions if they become necessary.
Watch WarningsEmergenciesComment -- mid-1960’sDrought of record for NJ -- 9/12/80 - 4/27/82 Started in northeastern NJ and expanded to central and northern Delaware basin -- 4/17/85 - 3/24/86Northeastern NJ --8/2/95-9/12/959/13/ /3/95Northeastern NJ --12/14/98 - 2/2/99-- Northeastern NJ (ended by record rains in Jan '99) --8/2/99 – 7/17/00 8/5/99 - 9/14/99 8/5/99 - 9/27/99 Southern NJ Northern NJ (Hurricane Floyd, Sept '99) 10/31/01-3/21/031/24/02 – 3/21/033/4/02 – 3/21/03 Some regions entered and left drought status slightly earlier. 9/13/ /14/05 5/8/06 – 7/3/06 9/8/10 – 10/26/10 -- Entire state in watch each time. Ended by statewide precipitation events. 9/23/15 -NE, C, CN regions
Relative Resource Importance to NJ Water Supply Reservoirs Unconfined Region NJ DRBC Rivers groundwater Northwest Central Northeast Southwest Coastal North Coastal South Major Source Minor Source Not a Regional Source
Regional Indicators Development started after 1999 events – two dry periods that could have been recognized as a single longer one. Wanted a better way to summarize regional hydrologic conditions. Need to concisely convey information to decision makers & the public. Designed to be updated quickly using real-time data. Indicators, not triggers.
Regional Indicators reservoirs (NJ & NY) groundwater levels streamflow precipitation
Reservoir Indicator compare current storage to rule curve.
Evaluation criteria based on a frequency analysis of a running 90- day deviation from normal. Streamflow Indicator
Groundwater Indicator Evaluation criteria is based on deviation from normal.
Precipitation Indicator Original Get 90-day surplus/deficit from MARFAC. Mentally overlay drought regions and make a judgement call.
Precipitation Indicator New ~2009 Download GIS coverage of 90-day % of normal precipitation from AHPS. Clip to drought regions. Calculate average % of normal in each region.
2015 Change in evaluation criterion of the AHPS % of normal precipitation Precipitation indicator based on % of normal wasn’t as useful as it should have been in evaluating water- supply droughts. Change to a frequency analysis. Percentages calibrated to past water-supply droughts. Will revise if not useful enough.
Current Status 9/27/15
Drinking-Water-Supply Status DEP staff look at hydrologic indicators and make a recommendation. DEP Commissioner has authority to declare watch & warning. The Governor declares a drought emergency. This is an evaluation of a water-supply (socioeconomic) drought.
Monitoring is always behind the curve. “We welcome the first clear day after a rainy spell. Rainless days continue for a time and we are pleased to have a long spell of such fine weather. It keeps on and we are a little worried. A few days more and we are really in trouble. The first rainless day in a spell of fine weather contributes as much to the drought as the last, but no one knows how serious it will be until the last dry day is gone and the rains have come again.” I.R. Tannehill, Drought: Its Causes and Effects, Princeton University Press, Princeton, New Jersey, 1947
What’s Next?