Drought Conditions/Hydrology

Drought Phases

With regard to Chester County, two agencies have the authority to declare drought conditions: the Pennsylvania Department of Environmental Protection and the Delaware River Basin Commission. In Pennsylvania there are 3 different drought phases.
The first is a

drought watch

. This is used to alert government agencies, public water suppliers, water users and the public regarding the onset of conditions indicating the potential for future drought conditions. Voluntary conservation of 5% are asked for affected areas.
If conditions worsen, the State may call a

drought warning

. This phase prepares for coordinated response to imminent drought conditions and potential water supply shortages. Voluntary conservation to reduce overall water uses by 10–15% are requested.
The final level is a

drought emergency

. All available resources are focused to ensure public health and safety with respect to water supplies. It is possible that mandatory restrictions on nonessential water uses could be enacted.
The Commonwealth of Pennsylvania uses five parameters to assess drought conditions: streamflows, precipitation, reservoir storage levels, ground water elevations, and a measure of soil moisture.
The Delaware River Basin Commission makes use of the percent of normal capacity of three large reservoirs in New York State to assist them with planning for and managing drought conditions. While they coordinate the efforts with the four states that are part of the Delaware River Basin (PA, DE, MD &NJ), the Basin Commission typically does not evaluate soil moisture or other criteria that Pennsylvania does consider.
For more information on droughts, please visit the the PA DEP's Drought Information Center, USGS's Pennsylvania Drought Condition Monitoring, and DRBC's Drought Information pages
Information on water conservation tips are available at the links below:

Drought Warning – Frequently Asked Questions

Are there any mandatory restrictions on water use under a state declared drought warning?

No – under the drought warning stage, water conservation or restrictions are not mandatory. Use of water for athletic fields , golf courses, agriculture, dust control, and other uses is currently allowed. Any user is strongly encouraged to conserve as much water as possible and to limit water use to the minimum amount required.

Can water utilities apply stricter regulations than the state?

Yes - if local conditions warrant, and with consultation with State agencies, water suppliers or municipal water utilities may place stricter regulations for water use, and activate a water rationing plan.

What conditions are evaluated when the State decides to issue a drought warning?

The Commonwealth uses five parameters to assess drought conditions. These include streamflows (compared to the same time for the period of record); precipitation (departure from normal, 30 year average precipitation); reservoir storage levels in a variety of locations (especially three New York City reservoirs in upper Delaware River Basin); groundwater elevations in a number of counties (comparing to past month, past year and historic record); and Palmer Drought Index, a measure of soil moisture computed by the National Weather Service.

Leaks in the Home - Conservation Tips

Leaks are the big water wasters in the home. Perform a water audit in your home.

Here is a simple way to check for leaks:

Read your meter TWICE. First at night after all water use has ended, and then again in the morning before your water use has begun. Subtract the first reading from the second reading to tell how much water (if any) leaked overnight. If you suspect a leak, check pipes, connections, faucets, toilets, etc. Have repairs made immediately.

Other Useful Tips:

  • Find the main water shutoff valve in your house, and clearly identify it. In the case of a pipe bursting, this will save a great deal of flood damage as well as thousands of gallons of water.
  • Insulate your water pipes. You'll get hot water faster plus avoid wasting water while it heats up.
  • Teach your children to conserve water. It's easier to start good water-using habits than to break wasteful habits later.

Winter Hydrology: Snowfall & Snowmelt

Throughout the winter, much of our attention is directed to weather forecasts to determine if snow is on the horizon, or how much snow fell in the past storm. Just as snowfall is a major source of water during the winter months, the snow on the ground (called the ‘snow cover’ or ‘snowpack’) is a significant storage of water during the winter months. When the snow cover melts much of the water flows over the land to streams, however there is some ground water recharge during the snowmelt as well. Even with the ground frozen, there are spaces where water can fill and flow down to the water table. This ground water recharge is critical to replenishing the aquifers for the upcoming spring and summer seasons.
There are a number of different ways to measure snowfall. One simple way is to use a snowboard and a ruler. A snowboard is simply a flat board that is placed on the ground. After the snowfall has accumulated, the depth is measured and recorded. Each time a measurement is taken, the snowboard is moved to the top of the snow. The rate of snowfall can be determined by taking measurements every hour or every six hours for example.
Another measurement of snowfall is to collect the snow and ice in a common cylindrical raingage, without the center measuring tube or top funnel. After the snow and ice are collected, the gage is placed in a warm area and melted. Then the melted precipitation is poured into the measuring tube and recorded. The result is the precipitation (as total water) in inches from the snowfall, which is the method that the CCWRA Volunteer Rainfall observers use.
The rule-of-thumb is that about 0.1 inches of precipitation (or water) results from every 1 inch of snow. A heavy, wet snow may be closer to 0.2 or 0.3 inches of precipitation to an inch of snow while a light, powdery snow may be less than 0.1 inch.

What Makes a Winter Storm?

Cold air:

below-freezing temperatures in the clouds and near the ground are necessary to make snow and/or ice.


to form clouds and precipitation. Air blowing across a body of water, such as a large lake or the ocean, is an excellent source of moisture.


something to raise the moist air to form the clouds and cause precipitation. An example of lift is warm air colliding with cold air and being forced to rise over the cold dome. The boundary between the warm and cold air masses is called a front. Another example of lift is air flowing up a mountain side.
For more information, check out the National Weather Service Winter Storm Safety web page.

How a Typical Nor’easter Forms

The classic winter storm in the Mid-Atlantic region is called a Nor'easter. A low pressure area off the Carolina coast strengthens and moves north. Wind-driven waves batter the coast from Virginia to Maine, causing flooding and severe beach erosion. The storm taps the Atlantic's moisture-supply and dumps heavy snow over a densely populated region. The snow and wind may combine into blizzard conditions and form deep drifts paralyzing the region. Ice storms are also a problem. Mountains, such as the Appalachians, act as a barrier to cold air trapping it in the valleys and adjacent low elevations. Warm air and moisture moves over the cold, trapped air. Rain falls from the warm layer onto a cold surface below becoming ice.