The Delmarva Peninsula comprises about 6,500 square miles on the Atlantic Coastal Plain and includes parts of Delaware, Maryland, and Virginia. The peninsula is underlain by unconsolidated sediments that range in thickness from a featheredge at the Fall Line (the northern boundary of the peninsula) to as much as 8,000 feet along parts of the Atlantic coast.Precipitation averages 43 inches per year, and streamflow averages 15 inches per year. About 672 inches of the average streamflow is overland flow, and the remaining 872 inches is ground-water discharge. The streams are generally perennial; however, low flow (7-day low flow at the 2-year recurrence interval) ranges from 0 to 1.16 cubic feet per second per square mile. Some low-flow data (in cubic feet per second per square mile) from 36 daily-record gaging stations, 25 partial-record gaging stations, and 120 miscellaneous sites are summarized for ready comparison.Drafts that may be made from specified amounts of storage with a chance of deficiency once in 5, 10, and 20 years, on a long-term average, are related to the median annual 7-day (7-day 2-year) low flow to permit preliminary estimates to Annual use of water on the peninsula in 1970 was about 137 mgd (million gallons per day), of which about 14 mgd was withdrawn from streams for irrigation supplies, and the remainder, 123 mgd, was withdrawn from the aquifers. About 75 percent of the ground-water supply was from the Quaternary aquifer and the water-table parts of the older aquifers. It is estimart;ed that the use of water on the peninsula by 2010 will be 260 mgd.The amount of fresh water that can be developed perennially on the peninsula is estimated to be 1,500 mgd. This amount is about 10 times the 1970 use and about six times the estimated use by the year 2010. Large long-term water supplies will probably have to be developed from the Quaternary aquifer. The perennial yield of this aquifer is estimated to be 1,000 mgd.
Queen Creek, considered in this paper, is a typical large desert wash. It rises in the Pinal Mountains near the mining town of Superior and enters the outwash‐plain at Black Point about three miles north of Florence Junction (see Fig. 1). Thence it passes over the desert in a southwesterly direction toward Chandler, spreads over the lowlands, and disappears. The flow of the stream consists almost entirely of storm‐water and is of the quick, flashy type common to the deserts of the Southwest. In ordinary years the stream is dry most of the time. Formerly the flood‐waters spread over the floor of the desert and did no harm. Now, however, they invade highly cultivated lands that are irrigated with water from Salt River or from wells, and cause serious damage to both crops and canals. The damage could be prevented by storing the stormwaters in a reservoir formed by a dam at or above Black Point.
The Mississippi embayment is part of a vast geologic and hydrologic province. Most of the region is underlain by aquifers that will yield large quantities of water to wells, so that ground water is the most readily available source of fresh water, Ground water having a dissolved-solids content of less than 500 ppm (parts per million) is generally available at depths of less than 1,000 feet, and water having a dissolved-solids content of less than 1,000 ppm is available in some places to depths of more than 2,000 feet. Iron is the most common troublesome chemical constituent in the ground water. The potential yield of the aquifers that underlie the region is estimated to be about 30,000 mgd (million gallons per day), of which about 3,000 mgd is presently being withdrawn. Water in varying amounts is also available from streams within the region. The amount of water which originates within the region and which leaves it as streamflow during a year averages about 90 million acre-feet (about 80,000 mgd). An additional 400 million acre-feet (about 360,000 mgd) leaves the region as streamflow during an average year, this amount having originated outside the region. The present withdrawals (1965) from streams within the region are about 1,700 mgd.
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