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The hydrogeology of the valley-fill aquifer system and surrounding watershed areas was investigated within a 23-mile long, fault-controlled valley in eastern Orange County, New York. Glacial deposits form a divide within the valley that is drained to the north by Woodbury Creek and is drained to the south by the Ramapo River. Surficial geology, extent and saturated thickness of sand and gravel aquifers, extent of confining units, bedrock-surface elevation beneath valleys, major lineaments, and the locations of wells for which records are available were delineated on an interactive map. Currently (2013), groundwater is the primary source of water supply in the study area. Several public water-supply systems withdraw groundwater from production wells in valley areas; elsewhere, domestic wells are used for water supply. Community-supply wells tap both sand and gravel and fractured bedrock aquifers; most domestic wells tap fracturedbedrock aquifers. Thick, saturated sand and gravel deposits are limited in areal extent but form several localized, productive aquifer zones within the valley-fill sediments. Hydraulic interconnection among these zones is largely untested. Finegrained lacustrine deposits form extensive confining units above some aquifer material. Till deposits that extend into valleys also confine sand and gravel or bedrock aquifers. The study area was divided into three sections—south, central, and north. The south section of the study area, from Harriman south to the Rockland County and New Jersey borders, includes the south-draining valleys of the Ramapo River and Summit Brook. South of the wide valley area at Harriman, the valleys are narrow and the valley-fill aquifers are largely untested; the most favorable aquifer conditions are likely at Arden and where major tributary streams enter the valley, between Southfields and We-Wah Lake. At Harriman, the Ramapo River valley fill has water-resource potential from ice-contact sand and gravel deposits. The central section of the study area encompasses the headwater drainage area of the Ramapo River, from Harriman to Monroe and Kiryas Joel. The valley-fill aquifer material is generally thin, mostly unconfined, and underlain by glacial till. Shallow production wells tap parts of this aquifer, and appear most productive when sited near surface-water bodies. Production wells in the section are frequently completed in the underlying bedrock. The north section of the study area encompasses the watershed of north-draining Woodbury Creek to just north of its confluence with Moodna Creek. The width of the valley bottom and type of valley-fill deposits vary considerably within the valley. The section likely has the greatest waterresource potential—both confined and unconfined aquifers are present and the village of Woodbury and town of Cornwall draw water supply from production wells. Aquifer potential appears most promising north of Central Valley, but several areas in this section are largely untested. Valley-fill aquifers are modest resources within the area, as indicated by the common practice of completing supply wells in the underlying bedrock rather than the overlying glacial deposits. Groundwater turbidity problems curtail use of the resource. However, additional groundwater resources have been identified by test drilling, and there are remaining untested areas. New groundwater supplies that stress localized aquifer areas will alter the groundwater flow system. Considerations include potential water-quality degradation from nearby land use(s) and, where withdrawals induce infiltration of surface-water, balancing withdrawals with flow requirements for downstream users or for maintenance of stream ecological health.

The hydrogeology of the valley-fill aquifer system along a 32-mile reach of the Susquehanna River valley and adjacent areas was evaluated in eastern Broome and southeastern Chenango Counties, New York. The surficial geology, inferred ice-marginal positions, and distribution of stratified-drift aquifers were mapped from existing data. Ice-marginal positions, which represent pauses in the retreat of glacial ice from the region, favored the accumulation of coarse-grained deposits whereas more steady or rapid ice retreat between these positions favored deposition of fine-grained lacustrine deposits with limited coarse-grained deposits at depth. Unconfined aquifers with thick saturated coarse-grained deposits are the most favorable settings for water-resource development, and three several-mile-long sections of valley were identified (mostly in Broome County) as potentially favorable: (1) the southernmost valley section, which extends from the New York–Pennsylvania border to about 1 mile north of South Windsor, (2) the valley section that rounds the west side of the umlaufberg (an isolated bedrock hill within a valley) north of Windsor, and (3) the east–west valley section at the Broome County–Chenango County border from Nineveh to East of Bettsburg (including the lower reach of the Cornell Brook valley). Fine-grained lacustrine deposits form extensive confining units between the unconfined areas, and the water-resource potential of confined aquifers is largely untested. Recharge, or replenishment, of these aquifers is dependent not only on infiltration of precipitation directly on unconfined aquifers, but perhaps more so from precipitation that falls in adjacent upland areas. Surface runoff and shallow groundwater from the valley walls flow downslope and recharge valley aquifers. Tributary streams that drain upland areas lose flow as they enter main valleys on permeable alluvial fans. This infiltrating water also recharges valley aquifers. Current (2012) use of water resources in the area is primarily through domestic wells, most of which are completed in fractured bedrock in upland areas. A few villages in the Susquehanna River valley have supply wells that draw water from beneath alluvial fans and near the Susquehanna River, which is a large potential source of water from induced infiltration.

Artificial-recharge experiments were conducted at East Meadow, N.Y., from October 1982 through January 1984. About 720 million gallons of reclaimed wastewater (tertiary-treated effluent) was applied to the upper glacial aquifer through seven recharge basins. An observation-well network was installed during 1985-87 to examine the physical and chemical properties of the plume derived from recharge water within the local flow system. Aquifer material in the study area was divided into three depth zones (upper glacial, intermediate, and Magothy) on the basis of plume chemistry and natural gamma-log data. Water-quality data indicate that the permeability of the intermediate zone varies locally, and gamma-log data indicate that the Magothy zone and parts of the intermediate zone within the study areahaveahigherclay contentand, thus, lower and more locally variable permeability than the upper glacial zone . Delineation of the recharge plume wasbased on chemical differences among recharge water, ambient ground water, and water affected by three other local influences. By March 1987, the recharge plume extended 6,500 feet downgradient from the recharge site and had a maximum width of 2,250 feet; its maximum depth below the water table was between 53 and 164 feet. The plume is more extensive in the upper glacial aquifer than in the underlying, less permeable Magothy aquifer. Chemical constituents of plume water were classified as either conservative or reactive. Chloride, a conservative solute, was used to indicate the maximum distance of recharge-plume movement and the relative reactivity of the other solutes. Sodium, sulfate, and boron were transported 80 to 100 percent as far as chloride. Calcium, magnesium, potassium, and alkalinity were transported 30 to 60 percent as far as chloride, and their movement appears to have been retarded by cation-exchange and sorption processes. Data from the unsaturated and saturated zones suggest that cation species in reclaimed water are exchanged primarily for hydrogen ion onto aquifer material. Sharp increases in hydrogen ion through this process are initially buffered by bicarbonate in the effluent. After the bicarbonate is exhausted, pH may decrease to less than 4 . Biological processes, such as nitrification, appear to affect nitrate concentrations as well as pH and alkalinity in the area affected by secondarytreated effluent from a sewage-disposal facility. Decomposition of organic matter may also affect pH in this area. Ground-water velocities within each depth zone, calculated from the distance traveled by chloride, were 3.4 ft/d in the upper glacial and intermediate zones, and 0.8 ft/d in the Magothy zone. These values are somewhat higher than those that would occur under natural conditions because recharge operations caused ground-water mounding and, thus, increased hydraulic gradients near the site. Velocities within the upper glacial zone, calculated from aquifer-test data and the distribution of road-salt leachate, were 2.0 to 3.2 fl/d. The recharge plume has migrated by advection and dispersion within the upper glacial zone, and conservative and minimally reactive components have begun to move ahead of and separate from the reactive components along the ground-water flowpath.