Artificial recharge by water spreading is practiced in several places in New Jersey. Rates of recharge ranging from 3,000 to 125,000 gallons per acre per day have been measured at the Perth Amboy Water Works, where artificial recharge of the Old Bridge sand, of upper Cretaceous age, has been practiced for more than 40 years. At the Duhernal development, which also draws from the Old Bridge sand, four or five million gallons daily is now derived from artificial recharge. This rate will probably increase with further lowering of the water table near the lake. For many years the Princeton Water Company has pumped water from a stream for recharging the Stockton sandstone, of Triassic age. The Lake Mohawk-Sparta Water Company spreads water underground by means of covered, gravel-filled ditches to recharge a shallow aquifer in its well field. The City of East Orange spreads the water from several small streams over parts of the intake area of the Quaternary beds supplying its wells. The estimated total recharge there is about two million gallons daily. Closely related to artificial recharge are those instances wherein well sites are chosen to take advantage of potential recharge from existing bodies of surface water. At the Borough of Manville no water spreading operations are conducted, but about three quarters of the water from its wells is derived by recharge from the Raritan River. The silting of water spreading areas may impair their effectiveness considerably. In some instances the growth of aquatic vegetation seems to reduce the ill effects of silting.