• A Review of Lake Ontario Water Quality with Emphasis on the 1981-1982 Intensive Years

      Three issues are currently being addressed with respect to the Lake Ontario ecosystem: eutrophication, contamination by toxic substances and fisheries management. This report reviews our present knowledge and understanding of Lake Ontario within the context of the first two issues. Although the report focuses on intensive studies carried out during 1981-82, it relies heavily on work from 1967 to 1985. I n preparing this report, it became obvious that many fundamental questions regarding the functioning of the Lake Ontario ecosystem remain unanswered. For example, although the total phosphorus load has been reduced to a level approaching the target load, those factors that control and/or limit algal biomass and productivity (e.g. is the lake phosphorus limited) remain poorly understood. Salmonid stocking of the lake continues in unprecedented numbers, yet our knowledge of foodweb interactions is very limited. Nitrate levels continue to rise significantly in the lake, but little effort has been made to identify the causes and consequences of this increase; the Water Quality Board has raised this issue in their 1985 and 1987 reports to the International Joint Commission.
    • Agricultural Issues: Eastern and Southern Experience

      Nonpoint Source Pollution: SCS Perspective (p. 239) Nonpoint Source Pollution from Plant Nutrients (p. 241) Nonpoint Source Pollution: Managing Nutrients a Key to Control (p. 244) Agricultural Land Treatment Project Planning for Off-Site Phosphorus Reduction (p. 245)
    • Agricultural Issues: Midwestern Experience

      Identifying Critical NPS Contributing Watershed Areas (p. 247) Gross Erosion Rates, Sediment Yields, and Nutrient Yields for Lake Erie Tributaries: Implications for Targeting (p. 251) Watershed Water Quality Programs: Lessons Learned in Illinois (p. 256) Prairie Rose Lake Rural Clean Water Program Project (p. 259) Agricultural Sources of Nitrate Contamination in a Shallow Sand and Gravel Aquifer in Eastern South Dakota (p. 264)
    • Agricultural Issues: Western Experience

      Agricultural Issues: The Nebraska Perspective (p. 269) Hydropolitical Solutions to Complex Nonpoint Salinity Pollution Problems in the Colorado River Basin (p. 273) Accumulation of Sediment, Nutrients, and Cesium-137 in Prairie Potholes in Cultivated and Noncultivated Watersheds (p. 274) Irrigated Agriculture and Nonpoint Source Pollution in the San Joaquin Valley of California (p. 276)
    • Agricultural N PS Control of Phosphorus in the New York State, Lake Ontario: Volume I - Delivery of Phosphorus to Lake Ontario from Cultivated Mucklands in Oak Orchard Creek Watershed Basin

      Cultivated mucklands in western New York State were investigated as a nonpoint source of phosphorus to Lake Ontario. The 70,500-ha Oak Orchard Creek watershed, which drains to Lake Ontario, was selected for the study area. It is located in Genesee and Orleans Counties, New York, and contains 3250 ha of heavily fertilized muck cropland on which predominantly vegetable crops are grown. The creek was monitored at several sites from May 1984 through April 1985 to determine the role of the mucklands in annual phosphorus loading to the lake. At an upstream site which drained approximately 10,200 ha, including the majority of the muck cropland, the creek load was 18,000 kg of total phosphorus with 75 percent of it as dissolved reactive phosphorus. Two-thirds of the annual load was delivered in the 3-month, high-flow period of February through April. Runoff during the late winter-early spring period appears to be the most important hydrologic factor in governing annual phosphorus loading from the mucklands, greater than either total precipitation or total runoff for the year. The pesticide DDT and its metabolites, DDE and DDD, were detected in muck soils and in creek suspended and bed sediments at this site. Although the annual loading rate of these compounds was thought to be relatively small, based on limited sampling, accumulation in the freshwater wetlands downstream which contain both a federal and a state wildlife refuge, could pose a hazard to sensitive species and warrants possible further investigation. A number of impoundments on the creek downstream of the mucklands, including the managed freshwater wetlands and two hydroelectric facilities, did not appear to significantly affect transport of phosphorus through the system during high-flow, late-winter months. In the largest impoundment, Waterport Pond, which is located 10 km from the creek mouth, internal loading of phosphorus from bottom sediments occurred during periods of hyrolirnnetic anoxia. Uptake and removal of bioavailable phosphorus by algae in Waterport Pond, rather than dilution by incremental flaw 1 was thought to account for a spatial phosphorus concentration gradient evident in summer months. The overall effect of Waterport Pond on annual phosphorus loading to Lake Ontario appeared to be removal of about 25 percent of the dissolved reactive form. Total phosphorus loading to Lake Ontario from Waterport Pond was 37. tonnes for the study year with 54 percent in the dissolved reactive form. Half of the load was delivered during the high-flaw months of March through May. A phosphorus load mass balance for Waterport Pond indicates that the greatest portion derives from the upper watershed containing the cultivated mucklands. Other smaller sources are the Village of Medina wastewater treatment plant and seasonal diversions of supplemental flow from the Erie Barge Canal. Control of phosphorus losses from the mucklands would appear to offer the most significant and cost-effective opportunities for loading reductions from this watershed.
    • Alternative Sources of Large Seasonal Ground-water Supplies in the Headwaters of the Susquehanna River Basin, New York

      Randall, Allan D.; Snavely, Deborah S.; Holecek, Thomas J.; Waller, Roger M.; USGS (1988-01-01)
      The northern divide of the Susquehanna River basin crosses 29 broad valleys that contain thick glacial deposits but are drained only by small headwater streams. Much groundwater could be withdrawn from sand and gravel deposits in these valleys with little immediate effect on streamflow. A digital model of the headwater reach of one typical valley suggests that pumping 10.8 million gal/day for 2 months every summer would lower the water table as much as 33 ft, cause the upper 1,900 ft of the stream draining the valley to go dry, and reduce streamflow downvalley by 1.2 million gal/day by the time pumping ceased. Saturated thickness of surficial sand and gravel exceeds 40 ft in about half the headwater valley reaches; the valley floor areas range from 0.2 to 9 sq mi. Seepage losses from small streams that carry runoff from adjacent till-covered uplands are a major source of recharge to aquifers in these valleys under natural conditions and would increase if the water table were lowered by seasonal withdrawals. Some aquifers beneath extensive clay layers in these and other valleys of the Susquehanna River basin may be partially independent of streams but not easily evaluated. (USGS)
    • An Atlas Displaying Some Older Water Quality Data for Comparisons with Recent Data

      Dobson, Hugh F. H.; National Water Research Institute (2001-04-01)
      This Atlas portrays the 'trophic status' of Lake Erie, mostly for the early years of monthly monitoring from 1966 to 1986 by ships and staff of Canada's Environment and Fisheries Departments from their Burlington laboratory called the Canada Centre for Inland Waters. The structure or distribution of water temperature is thoroughly displayed, because of its importance in relation to water quality and especially the water-masses of well-mixed character. Secchi transparency was quite variable and had a broad minimum, that is, maximum turbidity, in the 1970's decade. Data for chlorophyll a in the Central Basin during July and August indicated declining valued to 1986, the last year considered. That trend is probably a response to reduced external loading of phosphorus from urban and agricultural areas, which was the goal of the 1972 Great Lakes Water Quality Agreement between the United States and Canada. The author's diagrams of distributions of dissolved oxygen show trends in the vulnerable Central and Eastern hypolimnions. A recovery of dissolved oxygen by 1984 is not revealed. Particulate organic carbon, particulate nitrogen, and particulate phosphorus all declined (up to 1984), confirming the observed changes in the chlorophyll a data. The measurements of 'total phosphorus' in the water samples showed no change in the mid-summer values up to 1984. The early work by Dr. Julian Williams of the National Water Research Institute, on apatite and related minerals in Lake Erie sediments, could perhaps be extended to the water column. Mineral equilibria could be stabilizing the phosphorus concentrations in some fractions.
    • Areas Contributing Ground Water to the Peconic Estuary, and Ground-water Budgets for the North and South Forks and Shelter Island, Eastern Suffolk County, New York

      Schubert, Christopher E.; USGS (1998-01-01)
      The Peconic Estuary, at the eastern end of Long Island, has been plagued by a recurrent algal bloom, locally referred to as ?Brown Tide,? that has caused the severe decline of local marine resources. Although the factors that trigger Brown Tide blooms remain uncertain, groundwater discharge has previously been shown to affect surface-water quality in the western part of the estuary. A U.S. Geological Survey groundwater- flow model of the main body of Long Island indicates that a total of about 7.5 x 106 ft3/d (cubic feet per day) of freshwater discharges to the western part of the estuary, but the model does not include the ground-water flow systems on the North and South Forks and Shelter Island, which contribute significant amounts of freshwater to the central and eastern parts of the estuary. The need for information on freshwater discharge to the entire estuary prompted the U.S. Geological Survey to evaluate ground-water discharge from the North and South Forks and Shelter Island. Source areas that contribute ground water to the Peconic Estuary were delineated, and groundwater budgets for these areas were developed, to evaluate the distribution and magnitude of ground-water discharge to the central and eastern parts of the estuary. Contributing-area boundaries that were delineated coincide with the hydraulic boundaries of the fresh ground-water-flow systems of the North and South Forks and Shelter Island; these boundaries are of two types? external (saltwater bodies) and internal (groundwater divides). Hydrologic components that were evaluated include recharge from precipitation, public-supply withdrawal and return flow, and agricultural withdrawal. Values for each of these components were calculated or estimated for the individual freshwater flow subsystems that form each ground-water-budget area, then summed to obtain the total discharge of fresh ground water to tidewater. Ground-water discharge to the Peconic Estuary is about 3.8 x 106 ft3/d from the North Fork, 11 x 106 ft3/d from the South Fork, and 1.7 x 106 ft3/d from Shelter Island. The total contribution to the estuary from these areas is about 16 x 106 ft3/d?roughly twice the total contribution from the main body of Long Island. In contrast to the freshwater contribution from the main body of Long Island, which is concentrated near the head of the estuary, the contributions from the North and South Forks and Shelter Island are distributed along the east-west length of the estuary. Changes in water-table altitude and the resulting changes in total discharge to the Peconic Estuary were estimated from the relative changes in annual mean water level at observation wells. The 1985-95 interval included 7 years (1985-88, 1991- 92, 1995) of generally below-average water-table altitudes that presumably caused similar decreases in ground-water discharge to the estuary; intense Brown Tide blooms coincided with six of these years (1985-88, 1991, 1995), and localized blooms coincided with the remaining year (1992). Watertable altitudes in the remaining 4 years of the 1985-95 interval (1989-90, 1993-94) were nearly average or above average, and presumably produced comparably near-average or increased amounts of ground-water discharge to the estuary; none of these years saw any widespread Brown Tide blooms. Fluctuations in the amounts of ground-water discharge to the estuary appear to affect the occurrence of Brown Tide blooms, although the factors that trigger the blooms have not been determined.
    • Case Studies

      Highway Runoff Drainage Impacts (p. 387) Rock Creek Rural Clean Water Project: The Experiment Continues (p. 391) Regulating Nonpoint Sources of Pollution from Timber Harvesting - A Case History of the California Experience (p. 397) Agricultural Nonpoint Source Studies in Southeastern Watersheds: Field Monitoring and Farmer Surveys (p. 402) Vermont's LaPlatte River Watershed Project: Lessons Learned (p. 408)
    • Chemical Quality of Base Flow in 18 Selected Streams in the Upper Susquehanna River Basin, New York

      Hetcher, Kari K.; Miller, Todd S.; Komor, Steven C.; USGS (2004-01-01)
      The base-flow and runoff components of total streamflow at four selected sites in the upper Susquehanna River Basin in New York were calculated through hydrograph-separation techniques from long-term (1941-93) discharge records. Base flow was found to constitute more than 60 percent of the total annual flow of each stream. Base-flow samples were then collected at 18 stream sites several times during 2001 to define the chemical quality of base flow. The concentrations of selected common ions, nutrients, and pesticides were plotted in relation to the amount of agricultural land and carbonate bedrock in the drainage basin upstream of each site. Sites were selected at locations distant from and unaffected by development and urban areas. Twelve of the sites were again sampled in November 2001 for pesticide analysis. The predominant cations detected in the samples were calcium, magnesium, and sodium; the major anions were chloride, sulfate, and bicarbonate. The predominant nutrient was nitrate. Higher nitrate concentrations in the winter samples than in the summer samples are attributed to the seasonal decrease in plant growth and microbial activity in the streams during the winter, which allows nitrate to persist in the stream water. Lower nitrate concentrations in the summer samples probably result from nitrogen uptake by vegetation and microbial activity in the streams. Base-flow samples from the agricultural, carbonate-rich northern part of the study area had higher concentrations of most inorganic chemical constituents than those from the forested, noncarbonate (shale, siltstone, and sandstone) central and southern parts. The highest nitrate concentrations were in samples from subbasins dominated by agricultural land, and the lowest were in subbasins dominated by forest. The concentrations in samples from subbasins with forested as well as agricultural land were intermediate. Six pesticides were detected in samples from 10 of the 12 sites. All were herbicides. The highest concentrations of pesticides, and the most frequent pesticide detections, were in samples from agricultural subbasins and large main-stem subbasins with mixed land use and mixed bedrock geology. A correlation was indicated between land use and concentrations of atrazine and deethylatrazine. The concentrations of all six compounds were at least an order of magnitude lower than New York State and Federal water-quality standards. Ground water from four production wells in the villages of Afton, Sidney, Unadilla, and Otego was analyzed for chlorofluorocarbons (CFCs) to indicate the approximate age of the water in these wells and the potential for induced infiltration of river water. The water at two of these wells is probably between 26 and 50 years old; the ages of water at the other two wells could not be reliably estimated because of CFC contamination from a nonatmospheric source. The two wells for which CFC analysis gave reliable results (Afton and Otego) probably do not induce infiltration of river water into the aquifer.
    • Computation of Inflows and Outflows of Eight Regulated Lakes in the Oswego River Basin, New York, 1930-79

      Lumia, Richard; Moore, Richard B.; USGS (1983-01-01)
      Estimates of daily inflows and outflows of eight regulated lakes in the Oswego River basin and discharges of three rivers draining these lakes were computed and compiled for use in evaluated lake-regulation procedures in the basin 's stream and reservoir system and are stored on computer. This report includes a table of monthly flows at these sites from 1930-79. Computations were based on records from the 1930-79 water years. Daily net inflow estimates (lake inflow minus evaporation and possible groundwater seepage) were computed from the outflows and changes in lake storage. Lake storage was estimated from lake level data and elevation-capacity curves for each lake. A smoothing technique was applied to plots of daily lake levels before net inflows were computed. Where lake level or outflow data were missing, net flows were estimated from linear regression equations. Analysis of results indicates that: (1) smoothing the plots of daily lake levels significantly reduces random fluctuations resulting from seiche or wind action; (2) continuous lake storage recorders provide a more reliable record than staff gages (once-daily, lake level readings) for computing daily changes in lake storage; and (3) the effect of smoothing decreases as the computational period is increased. (USGS)
    • Conesus Lake Fish Stock Assessments 2001-2009

      Sanderson, Matthew J.; NYS DEC (2014-10-20)
      Warm water fisheries assessments using standard gangs of gill nets were conducted in Conesus Lake in September of 2001, 2004, and 2009. The purpose of the surveys was to assess the fish community; the contribution of stocked fingerlings to the walleye (Sander vitreus) population; estimate population characteristics of walleye, smallmouth bass (Micropterus dolomieui), and northern pike (Esox lucius); compare fish community structure to previous surveys; and guide the development of appropriate management recommendations. From the 1990’s to the 2000’s, species dominance shifted from walleye to sunfish (Lepomis, sp.), and yellow perch (Perca flavescens) went from being a major component of the fish community in 1991 to a minor component in 1997, to nearly absent in 2004. Brown bullhead (Ameirus nebulosus) became an increasingly larger component of the fish community in the 2000’s. The walleye population during the 2000’s had an abundance of larger, older fish in excellent condition. Despite extensive migratory spawning runs in the inlet streams that could be producing fry that potentially recruit to adults, the walleye population is mainly sustained by stocked fingerlings. While they are growing slower than in the 1990’s, survival and recruitment of the stocked fingerlings remains good. Slower growth and lower condition could be a sign that the alewife population in Conesus Lake is declining, but no definitive statement regarding the alewife population can be made until further hydroacoustic surveys of the forage community are conducted. Because of discrepancies of scale ages among readers, walleye age and growth analyses for these surveys should be viewed cautiously, and otoliths should be used to age walleye in future surveys. The fishing quality for Conesus Lake walleyes should remain very good for several years. The smallmouth bass population by 2009 had an abundance of larger, older fish in fair condition. The 2007 and 2006 year classes appear to be strong, but individual fish of these year classes may grow slowly and be in less than desirable condition. The fishing quality for Conesus Lake smallmouths should remain good for several years as the fish from these year classes mature and grow. Northern pike appear to be moderately abundant. The recent maintenance of appropriate lake water levels during early spring have provided adequate flooding of constructed marshes in the Conesus Inlet Wildlife Management Area. This appears to have resulted in successful spawning, fry production, survival, and recruitment of northern pike. Adult pike, while fast growing, are in below average condition in Conesus Lake. The yellow perch decline in abundance following a late 1970’s alewife (Alosa pseudoharengus) invasion continued during the 1991- 1997 period and remained at this low level from 2001 to 2009. Alewife gill net CPUE varied greatly from 1985 to 2001 and remained at a consistent low level since 2001. While relatively large, yellow perch are in poor condition and alewives are smaller than average and in poor condition. Rock bass (Ambloplites rupestris) and bluegill (Lepomis macrochirus) relative abundance doubled from 2001 to 2009, while pumpkinseed (Lepomis gibbosus) abundance showed little change. Survival and growth appears to be consistent for all three species. Growth was above average for all three species, but condition was poor for rock bass and moderately poor for pumpkinseed and bluegill. Rock bass size structure was poor and few preferred sized 2 pumpkinseeds and bluegills were sampled. Size quality in bluegills declined from 1991-1997 levels. It is recommended that all current management actions be continued, 50 day walleye fingerlings be stocked annually over five years, the success of stocked 50 day walleye fingerlings be evaluated, and new objectives be developed in a revised Conesus Lake fisheries management plan.
    • Contributed Papers

      The Effects of Carbonate Geology on Urban Runoff: Water Quality Aspects (p. 499) Using In-Stream Monitoring Stations To Evaluate Pollution from Urban Runoff (p. 502) Conservation Service Field Office Program Delivery by Hydrologic Areas (p. 506) Agricultural Land Improvement and Water Quality in South Central Minnesota (p. 508)
    • Cost Effectiveness of the US Geological Survey's Stream-gaging Program in New York

      Wolcott, Stephen W.; Gannon, William B.; Johnston, William H.; USGS (1986-01-01)
      The U.S. Geological Survey conducted a 5-year nationwide analysis to define and document the most cost effective means of obtaining streamflow data. This report describes the stream gaging network in New York and documents the cost effectiveness of its operation; it also identifies data uses and funding sources for the 174 continuous-record stream gages currently operated (1983). Those gages as well as 189 crest-stage, stage-only, and groundwater gages are operated with a budget of $1.068 million. One gaging station was identified as having insufficient reason for continuous operation and was converted to a crest-stage gage. Current operation of the 363-station program requires a budget of $1.068 million/yr. The average standard error of estimation of continuous streamflow data is 13.4%. Results indicate that this degree of accuracy could be maintained with a budget of approximately $1.006 million if the gaging resources were redistributed among the gages. The average standard error for 174 stations was calculated for five hypothetical budgets. A minimum budget of $970,000 would be needed to operated the 363-gage program; a budget less than this does not permit proper servicing and maintenance of the gages and recorders. Under the restrictions of a minimum budget, the average standard error would be 16.0%. The maximum budget analyzed was $1.2 million, which would decrease the average standard error to 9.4%. (Author 's abstract)
    • Cross Boundary Nonpoint Source Pollution: The Implications

      Great Lakes Pollution from Land Use Activities (p. 487) Irrigation Return Flows and Salinity Problems in the Colorado River Basin (p. 495) Agricultural Nonpoint Source Pollution in the Midwest (p. 497)
    • Data Availability and Needs

      A Data Management System to Evaluate Water Quality Impacts of Nonpoint Source Pollution Control (p. 429) Development of a Nonpoint Source Data Center (p. 433) Water Quality Data And Urban Nonpoint Source Pollution: The Nationwide Urban Runoff Program (p. 437) The RFF National Data Base for Nonpoint Source Policy Assessments (p. 442)
    • Determination of Traveltime in the Delaware River, Hancock, New York, to the Delaware Water Gap by Use of a Conservative Dye Tracer

      White, Kirk E.; Kratzer, Todd W.; USGS (1994-01-01)
      Traveltime of a soluble substance was determined for a 120-mile reach of the Delaware River from the confluence of the East Branch Delaware River and the West Branch Delaware River at Hancock, N.Y. to the Delaware Water Gap. Dye studies were conducted at the 85-95 percent and the 25-30 percent flow durations. Discharges ranged from 500-1,740 cubic feet per second during the 85-95 percent flow duration and 3,070-7,500 cubic feet per second for the 25-30 percent flow duration. The data were used to develop a set of time-concentration curves that would enable estimation of the traveltime of a spill at any point in the river within the study reach for 10 flow durations. The leading edge of a contaminant spill at Buckingham Access would take about 70 hours to reach the Delaware Water Gap when flows are at the 30-percent flow duration. The trailing edge (location of the dye cloud when concentrations would decrease to 10 percent of the peak concentration) would take about 50 hours after the arrival of the leading edge.
    • Distribution and Source of Barium in Ground Water at Cattaraugus Indian Reservation, Southwestern New York

      Moore, Richard B.; Staubitz, Ward W.; USGS (1984-01-01)
      High concentrations of dissolved barium have been found in ground water from bedrock wells on the Seneca Nation of Indians Reservation on Cattaraugus Creek in southwestern New York. Concentrations in 1982 were as high as 23.0 milligrams per liter , the highest found reported from any natural ground-water system in the world. The highest concentrations are in a bedrock aquifer and in small lenses of saturated gravel between bedrock and the overlying till. The bedrock aquifer is partly confined by silt, clay, and till. The high barium concentrations are attributed to dissolution of the mineral barite (BaSO4), which is present in the bedrock and possibly in overlying silt, clay, or till. The dissolution of barite seems to be controlled by action of sulfate-reducing bacteria, which alter the BaSO4 equilibrium by removing sulfate ions and permitting additional barite to dissolve. Ground water from the surficial, unconsolidated deposits and surface water in streams contain little or no barium. Because barium is chemically similar to calcium, it probably could be removed by cation exchange or treatments similar to those used for water softening. (USGS)
    • Economics of Nonpoint Source Pollution

      Economics: Nonpoint Source Pollution Impacts (p. 229) Economics of Nonpoint Source Pollution Control: Lake Tahoe, California/Nevada (p. 232) Controlling Agricultural Runoff: Government's Perspective (p. 234) Soil Erosion as a Nonpoint Source - A Farmer's Perspective (p. 237)
    • Effects of Acid Deposition on Dissolution of Carbonate Stone During Summer Storms in the Adirondack Mountains, New York, 1987-89

      Schuster, Paul F.; Reddy, Michael M.; Sherwood, Susan I.; National Park Service; USGS (1994-01-01)
      This study is part of a long-term research program designed to identify and quantify acid rain damage to carbonate stone. Acidic deposition accelerates the dissolution of carbonate-stone monuments and building materials. Sequential sampling of runoff from carbonate-stone (marble) and glass (reference) microcatchments in the Adirondack Mountains in New York State provided a detailed record of the episodic fluctuations in rain rate and runoff chemistry during individual summer storms. Rain rate and chemical concentrations from carbonate-stone and glass runoff fluctuated three to tenfold during storms. Net calcium-ion concentrations from the carbonatestone runoff, a measure of stone dissolution, typically fluctuated twofold during these storms. High net sulfate and net calcium concentrations in the first effective runoff at the start of a storm indicated that atmospheric pollutants deposited on the stone surface during dry periods formed calcium sulfate minerals, an important process in carbonate stone dissolution. Dissolution of the carbonate stone generally increased up to twofold during coincident episodes of low rain rate (less than 5 millimeters per hour) and decreased rainfall (glass runoff) pH (less than 4.0); episodes of high rain rate (cloudbursts) were coincident with a rapid increase in rainfall pH and also a rapid decrease in the dissolution of carbonate-stone. During a storm, it seems the most important factors causing increased dissolution of carbonate stone are coincident periods of low rain rate and decreased rainfall pH. Dissolution of the carbonate stone decreased slightly as the rain rate exceeded about 5 millimeters per hour, probably in response to rapidly increasing rainfall pH during episodes of high rain rate and shorter contact time between the runoff and the stone surface. High runoff rates resulting from cloudbursts remove calcium sulfate minerals formed during dry periods prior to storms and also remove dissolution products formed in large measure by chemical weathering as a result of episodes of low rain rate and decreased rainfall pH during a storm.