New York Rural Water Association

Here in New York State we on average have ample precipitation. However, as we all know, there are variations in weather patterns that result in periods of drier weather. Based upon data from the National Climatic Data Center, New York State regularly experiences moderate drought conditions every 2 to 5 years. These moderate droughts typically last for a few months. Of much more concern is the fact that we also experience severe to extreme droughts every 10 to 20 years. These can last nearly a year to over two years. All water suppliers should prepare some type of drought response plan that addresses water conservation, water use restrictions, and alternate water supply sources. This plan can be part of an overall emergency plan. Water suppliers should declare successive drought stages with increasing restrictions. These drought stages could look something like this:

Local Drought Stage	Example Actions
I (Watch)	Water suppliers cut back on water use (flushing, street cleaning, etc.). Water suppliers fix all leaks and wastes of water and conduct leak survey. Water suppliers correct obsolete rate structures. Water suppliers urge customers to conserve water.
II (Warning)	All items from Stage I. Water suppliers intensify voluntary water conservation measures and prepare the public for mandatory measures. Water suppliers make provisions for utilizing emergency sources of supply.
III (Emergency)	All items from Stages I and II. Prohibit washing of vehicles using water from the system except at washing operations that recirculate water. Prohibit use of water from the system to wash street, sidewalk, driveway, etc. Prohibit use of water from any source for any ornamental purpose. Restrict use of water from the water system to water lawns, trees, shrubs, gardens, or golf course greens and tees to limited hours in evening. Nonresidential users shall reduce consumption by no less than 15%. Tap emergency sources of water.
IV (Disaster)	All items from Stage I, II, and III. Prohibit use of water from the water system to fill or maintain the water level in any pool. Prohibit use of water from the water system to water any lawn, golf course, ornamental shrubs or plants. Nonresidential users shall reduce consumption by no less than 25%. Institute emergency measure that could include mandatory installation of water saving devices, etc.

Triggers For Local Drought Stages

What should be the mechanism that triggers a water supplier to designate a particular local drought stage? Should it be based upon state issued drought advisories? Should it be based upon the water supplier’s source water levels? Both are important, but I believe that the latter is a more important factor to consider. Unfortunately, the majority of water suppliers using groundwater do not maintain water level monitoring data to help them determine if they are reaching critical source water levels. Even if such systems do monitor water levels, the critical water levels in question are often not known.

State Drought Advisories

The NYSDEC will declare drought advisories for nine different state drought management regions (see Figure 1). The state specifies the regional drought stage based upon stream flows, precipitation, lake and reservoir storage levels, groundwater levels, and the Palmer Drought Index, a measure of soil moisture. I believe that water suppliers should consult with state drought advisories. However, water suppliers should not solely use the state advisories to declare local drought stages. This is particularly true for water systems relying upon groundwater sources.

Figure 1. Drought Management Regions.

As indicated in Figure 2, the U.S. Geological Survey (USGS) maintains a network of 27 observation wells for drought monitoring. Data from most of these wells is available online through http://ny.water.usgs.gov/. There are two chief drawbacks to using these observation wells in place of local source water data. First, there are a very limited number of wells, particularly across upstate New York. Most counties do not have an observation well in the network. Drought conditions are not necessarily uniform through the large regions. Second, the observation wells target shallow groundwater (the majority of the USGS observation wells in upstate New York are less than 25 feet deep). Most public water systems rely upon deeper sand and wells, confined aquifer wells, or bedrock.

Figure 2. USGS Observation Wells.

Local Source Water Levels

Establishing critical "trigger" water levels is comparatively easy for surface water sources. Surface water levels can be readily observed and the amount available can be calculated. However, water levels in wells are not as readily measured and the relationship between water level drawdown and well yield is often complex. The remainder of this article focuses on how groundwater systems can establish critical water levels for drought response.

Determining Critical Groundwater Levels

There are no published methods of determining critical groundwater levels for drought stages. As the NYSDOH indicates in the Guidelines for the Preparation of an Emergency Plan for Community Water Supplies "there are no simple formulas applicable to every geological condition, hydrological condition, and type of well construction to determine critical water levels…" I have looked into how a groundwater system could derive critical groundwater levels and have formulated a possible methodology that I describe as follows.The first step in determining the critical groundwater levels that should be used to declare local drought stages is to research your system well data and determine the depth of the pump intake and the type of aquifer. This information is critical to know. Second, you must determine the maximum static water level for the well. This is the highest water level observed in your well during non-pumping conditions. If you have not been monitoring the water levels, you can initially use the static level on the well completion report completed by the driller. However, this static level is not likely to be the highest static level experienced in the well and this number should only be used until you have been better determined the maximum static level in the well.

Third, you must calculate the maximum safe available drawdown for the well. For unconfined sand and gravel aquifers, this is the difference between the depth of the pump intake and the maximum static level (Figure 3). For confined aquifers, it is the difference between the depth to the top of the confined aquifer and the maximum static level (Figure 4). For bedrock wells it is the difference between the depth of uppermost water-bearing fracture zone and the maximum static level (Figure 5).


Figure 3.	Figure 4.

Figure 5.

Next, begin monitoring pre-pumping (static) and pumping water levels on a daily basis. If necessary install a stilling tube and use an electric water level indicator or have a pressure transducer probe installed in the well. Calculate the present overall drawdown by subtracting the maximum static water level from the present pumping water level.Finally, divide the present overall drawdown by the maximum safe available drawdown. If this ratio is between 0.7 and 0.8, you should consult the state’s regional drought stage and determine if a local watch or warning is in order. A ratio of 0.8 to 0.95 suggests that a drought emergency exists and water restrictions may be in order. A ratio of greater than 0.95 could be indicative of an imminent loss of pumping ability and thus represents a potential disaster. In addition, if at any time the observed pumping level reaches within 5 feet of the pump intake, I would suggest initiating a drought emergency and reduce use of the well. Keep in mind that these numbers are my own invention and should only be used as guidelines.

Final Thoughts

If you have any questions about drought monitoring, please feel free to give me a call at 1-888-NYRURAL or email me at Winkley@nyruralwater.org. I would be pleased to help you set up a monitoring program to protect your valuable groundwater resources!