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USGS1964

Geology and hydrology of the West Milton area, Saratoga County, New York

This report describes the geology, ground-water conditions, streamflow characteristics, and quality of water in the West Milton area, Saratoga County, N.Y. The West Milton area is in the east-central part of New York in the hilly region that forms a transition zone between the Adirondack Mountains and the Hudson-Mohawk valley lowland. Bedrock underlying the area consists of crystalline rocks of Precambrian age and sandstone, dolomite, limestone, and shale formations of Cambrian and Ordovician age. The formations have been moderately folded and have been displaced as much as several hundred feet' along at least three northeast-trending normal faults. The bedrock is overlain in nearly all parts of the area by a layer of unconsolidated deposits which ranges in thickness from a few feet to more than 200 feet. The unconsolidated deposits are of Pleistocene age and consist of unstratified materials (till) laid down by glacial ice at stratified sediments deposited by glacial meltwaters. The topography of the bedrock surface differs greatly from the topography of the land surface. Although not evident in the present topography, at least two channels, cut in bedrock by preglacial streams, pass through the area. Ground-water supplies adequate to satisfy domestic requirements can be obtained from wells in any part of the area. Large ground-water supplies may be taken from coarse-grained stratified deposits comprising two aquifers in the valley of Kayaderosseras Creek. The Atomic Energy Commission has pumped as much as 1 mgd from a horizontal well drawing from the uppermost aquifer which is composed of flood-plain deposits. Part of the water yielded by this well during extended periods of pumping is induced flow from the creek. Three nearby vertical wells drilled by the Commission comprise a separate well field capable of yielding at least 2 mgd and possibly as much as 3 mgd from the deeper stratified deposits underlying the valley. A pumping test showed that at near the center of this well field the coefficient of transmissibility is about 125,000 gpd per ft and the coefficient of storage is about 0.0003. The water obtained from the sand and gravel has a hardness of about 125 ppm and contains about 150 ppm of dissolved solids. Most of the Government reservation is drained by Glowegee Creek, one of the larger tributaries of Kayaderosseras Creek. The average streamflow of Kayaderosseras Creek at West Milton is 141 cfs or about 1.5 cfs per sq. mi. The monthly mean discharge has ranged from a low of 21.7 cfs in September 1958 to a high of 866 cfs in March 1936, and the annual mean discharge has ranged from 94.5 cfs in 1941 to 198 cfs in 1952. The mean annual flood is 1,740 cfs and the 50-year flood is 5,300 cfs. Streamflow data have been collected on Glowegee Creek since 1948 at a station 0.5 mile south of West Milton. The average streamflow of Glowegee Creek at this station is 41 cfs or about 1.5 cfs per sq mi. The mean annual flood is 740 cfs and the 50-year flood is 2,250 cfs. The quality of the water in both Kayaderosseras Creek and Glowegee Creek is satisfactory for public supply and most industrial purposes. The mineral content of both streams is low--the dissolved-solids content averaging about 93 ppm in Kayaderosseras Creek and about 131 ppm in Glowegee Creek. The average hardness of water in Kayaderosseras Creek and Glowegee Creek is 68 ppm and 102 ppm, respectively. During periods of low flow, suspended sediment discharge in both streams is less than 10 tons per day, but during periods of high flow, the sediment discharge has been as great as 163 tons per day in Glowegee Creek and 437 tons per day in Kayaderosseras Creek.

Water Supply Paper↗
USGS1964

Apparatus and techniques for measuring bedload

The need for accurate determinations of the total sediment discharge of particles of bedload size has prompted this investigation of available and possible measuring apparatus and procedures. The accuracy of measurements of sediment discharge made with trap-type samplers is affected by the variability of sampler efficiency, by the oscillatory variation of bedload discharge, and by sampler placement. Equations that were developed for determining total discharge from measured bedioad discharge and measured suspended-sediment discharge are simplest if the bedload apparatus measures only the true bedload. Early bedload samplers are generally unsatisfactory. Recently developed or suggested apparatus include various improved samplers of the pressure-difference type, a pumping sampler, a magnetic sampler, acoustical instruments that measure the magnitude of the sound of particle collisions, an ultrasonic bedload sampler designed to measure and integrate electronically the concentration and velocity, and a tiltmeter designed to measure the total sediment discharge from the ground tilt that results from the passage of flow. All the pressure-difference samplers are improvements over early samplers, but none are void of the inherent shortcomings of trap-type apparatus; probably the Sphinx (Dutch) and VUV (Hungarian) samplers are the most satisfactory. The acoustical instruments are capable of measuring only the relative discharge. The ultrasonic sampler and the tiltmeter are not adequate without further development. Some new possible apparatus and means for measuring or aiding in measuring bedload discharge are small pit samplers, ultrasonic sounders, pressure transducers, and photography. A small pit sampler for measuring bedload discharge was designed to provide self-placement and portability ; however, its practicability and efficiency are undetermined. Exploratory films show that by using slowmotion photography the discharge of particles larger than about pea size can be determined provided the flow is clear; however, photography generally is not practical. Ultrasonic sounders provide continuous and accurate data on bed configuration and dune movement for use in equations that were developed for computing the bedload discharge. Computations with the equations indicate that the interpretation of the sounding data needs further study. Pressure transducers placed beneath the bed surface possibly can be used to provide information on dune movement; however, their installation would be difficult. The time required for collecting data on bed configuration and dune movement throughout a cross section could be substantially reduced by using several transducers simultaneously in conjunction with an ultrasonic sounder. A modified ultrasonic sounder that provides information on the shape and velocity of large particles and a method for determining the discharge of such particles were proposed; the method seems most feasible for particles of high sphericity.

Water Supply Paper↗
USGS1964

Geology and ground-water resources of Nobles County, and part of Jackson County, Minnesota

The area described in this report is in southwestern Minnesota, about 130 miles southwest of Minneapolis and St. Paul. It includes; Nobles County and the western tier of townships in Jackson County, a total of 864 square miles. Worthington, the Nobles County seat, is the largest city in the area, having a population of 9,015 persons (1960 census). Farming is the leading occupation, and food processing is the major industry. Critical water shortages have occurred in several parts of the area. The climate is characterized by mild, subhumid summers and relatively long, severe winters. Mean monthly temperatures range from 15.1 °F in January to 73.3 °F in July. The mean annual precipitation is 26.75 inches. The crest of the Coteau des Prairies, a broad highland belt, traverses Nobles County from northwest to southeast. Three glacial end moraines and their associated ground moraines trend south to southeast across the area. Altitudes range from about 1,820 feet on the crest of the coteau in the northwestern part of the area to about 1,390 feet above mean sea level in the Jack and Okabena Creek valleys in the northeast. The Mississippi-Missouri River drainage divide crosses the area from north to east. The Gary outer end moraine trends southeast through central Nobles County. East of this moraine the land is poorly drained and contains numerous lakes and swamps; west of this moraine the land is well drained and contains few, if any, undrained depressions. Within the area, granite and Sioux Quartzite of Precambrian age are overlain by Cretaceous strata, except locally in the northeast and northwest parts of the area where the quartzite is directly overlain by glacial drift. The Cretaceous strata are composed of interbedded shale, siltstone, and sandstone. The surface of the area is composed of Pleistocene deposits of glacial drift and some thin, patchy deposits of Recent age. Bedrock is not known to crop out in the area. The drift ranges in thickness from about 150 feet in the southwest and northeast corners to about 500 feet on the highest part of the Coteau des Prairies. The Precambrian granite is not a source of ground water in this area. The Sioux Quartzite yields moderate supplies in adjacent counties to the north and west, but because of its sporadic occurrence it does not constitute an important water source in this area. The Cretaceous sandstone units are a secondary source of ground water and yield adequate supplies 'to at least 24 farm wells, which range in depth from 283 to 586 feet below land surface. The primary source of ground water in the Nobles-Jackson County area is the glacial drift. Buried outwash deposits supply water to 7 of the 10 municipalities and to most of the farms in the area. Two Worthington city wells, completed in a buried outwash deposit underlying East Okabena dry lake bed, were tested for short periods at 500 gallons per minute. The estimated coefficient of transmissibility for the aquifer at one of the wells was 70,000 gpd (gallons per day) per ft. The buried outwash deposits may occur anywhere within the drift from about 15 feet below land surface to bedrock which is as much as 500 feet below land surface. The outwash ranges from a fraction of a foot to more than 25 feet in thickness where permeable; below the water table it generally will supply ample quantities of water to properly constructed wells. Surflcial outwash deposits fill the valley bottoms and form the terrace deposits associated with the present-day drainage channels. The thicker, more extensive, and continuous deposits occur in the proglacial stream channels that drained the fronts of the ice sheets rather than in those channels that now drain the backs of the moraines. The surflcial outwash deposits generally are made up of sand, gravel and some silt and clay, and range in thickness from 0 to more than 60 feet; they range in width from a few feet in the narrow tributaries to about one mile in the larger stream valleys. Four municipalities and many farms obtain part or all of their water supplies from surficial outwash. An Adrian municipal well, completed in this source, was pumped at a rate of 400 gpm. At the confluence of two streams which drain Ocheda Lake in southeastern Nobles County, the sand and gravel section is more than 60 feet thick in places. Results of a pumping test here showed an average coefficient of transmissibility of 150,000 gpd per ft. Coefficients of transmissibility may be as much as 500,000 gdp per ft in the thickest part of the deposit if the permeability of the sand and gravel is uniform. Recharge to the surflcial outwash deposits is relatively rapid; it is slower to the buried outwash deposits where the descending water must percolate through till of low permeability before entering the aquifers. The quality of water in the Precambrian crystalline rocks, the Cretaceous strata, and the buried Pleistocene aquifers is poor. Chemical analyses of 22 water samples showed that dissolved solids ranged from 1,100 ppm (parts per million) to 3,050 ppm. Water from the surficial outwash deposits is good by comparison; dissolved solids in water from these aquifers ranged from 425 to 870 ppm.

Minnesota↗
USGS1906

Report of progress of stream measurements for the calendar year 1905, Part XI, Colorado River drainage above Yuma

The hydrographic work of the United States Geological Survey includes the collection of facts concerning and the study of conditions affecting the behavior of water from the time it reaches the earh as rain or snow until it joins the oceans or great navigable rivers. These investigations became a distinct feature of the work of the Survey in the fall of 1888, when an instruction camp was established at Embudo, N. Mex. The frist specific appropriation for gaging streams was amde by the act of August 18, 1894, which contained an item of $12, 500 'for gaging the streams and determining the water supply of the United States, including the investigation of underground currents and artesian wells in the arid and semiarid sections.'

Water Supply Paper↗
USGS1964

Summary of floods in the United States during 1959

This report describes the most outstanding floods that occurred in the United States during 1959. The floods of January-February in Ohio and adjacent States were the most outstanding floods of the year 1959 with respect to area affected, number of streams having maximum discharge of record, rare occurrence of peaks, and great amount of damage caused. Floods in the Rock River basin in southern Wisconsin and northern Illinois during late March and early April produced maximum stages and discharges on many streams. The Rock River at Watertown, Wisc., was the highest in 40 years and Lake Mendota at Madison, Wisc., reached its maximum stage since 1916. Many towns were flooded and thousands of persons were forced from their homes. What is possibly the greatest 24-hour rainfall ever to be noted in Iowa fell August 5-6. The resulting floods inundated an 80-block area in Fort Madison, Iowa, and caused damage estimated at $600,000 in the city. A total of 130,000 acres of land was inundated. Major floods occurred in Texas in the upper Trinity, middle Brazos, middle Colorado, upper Guadalupe, and upper Nueces River basins in early October, following heavy general rains that covered most of Texas. The peak stage on North Bosque River near Clifton was the highest known since 1887. More than \$1 million in damage was reported for Houston. In addition to the 4 floods mentioned above, 22 others of lesser magnitude are considered important enough to report in this annual summary.

Water Supply Paper↗
USGS1964

Ground-water resources of north-central Connecticut

The term 'north-central Connecticut' in this report refers to an area of about 640 square miles within the central lowland of the Connecticut River basin north of Middletown. The area is mostly a broad valley floor underlain by unconsolidated deposits of Pleistocene and Recent age which mantle an erosional surface formed on consolidated rocks of pre-Triassic and Triassic age. The mean annual precipitation at Hartford, near the center of the area, is 42.83 inches and is uniformly distributed throughout the year. The average annual streamflow from the area is about 22 inches or about half the precipitation. The consolidated water-bearing formations are crystalline rocks of pre-Triassic age and sedimentary and igneous rocks of the Newark group of Triassic age. The crystalline rocks include the Middletown gneiss, the Maromas granite gneiss, the Glastonbury granite-gneiss of Rice and Gregory (1906), and the Bolton schist which form the basement complex and the Eastern Upland of north-central Connecticut. Enough water for domestic, stock, and small commercial use generally can be obtained from the crystalline rocks. Recoverable ground water occurs in the interconnected joints and fracture zones and is yielded in amounts ranging from 29 to 35 gpm (gallons per minute) to wells ranging in depth from 29 to 550 feet. The sedimentary rocks of Triassic age underlie all the Connecticut River Lowland and are predominantly arkosic sandstone and shale. Water supplies sufficient for domestic, stock, and small commercial use can be obtained from shallow wells penetrating these rocks, and larger supplies sufficient for industries and smaller municipalities can probably be obtained from deeper wells. Reported yields range from ? to 578 gpm; the larger yields are generally obtained from wells between 300 and 600 feet in depth. Yields are larger where the overlying material is sand and gravel or where the rocks are well fractured. The igneous rocks of Triassic age are basalt and have water-bearing characteristics similar to the crystalline rocks. The unconsolidated deposits comprise ground-moraine and drumlin deposits, ice-contact deposits, outwash-plain and valley-train deposits, and glaciolacustrine and associated delta deposits of Pleistocene age, as well as dune deposits, good-plain deposits, and swamp deposits of Recent age. Ground-moraine deposits occur throughout the area but yield only small quantities of water. The ice-contact deposits consisting mostly of sand and gravel form kames, kame terraces, and crevasse fillings and are the surface deposits in three extensive areas along the eastern margin of the Connecticut River Lowland. The deposits in most places are saturated and, where they consist of well-sorted material, are highly permeable, yielding as much as 750 gpm to properly constructed wells. Outwash-plain and valley-train deposits and bodies of undifferentiated outwash underlie the surface in the eastern and southern parts of the area. These deposits consist of well-sorted sand and silt and some pebble gravel ranging in thickness from nearly zero to more than 225 feet in places. The thicker deposits are an important source of moderate supplies of ground water. Screened wells of moderate depth commonly yield about 150 gpm, but some yield as much as 400 gpm. Bodies of buried outwash deposits of irregular size and shape occur in the bottoms of some of the filled bedrock valleys. They seldom are more than 20-30 feet thick. Their permeability Is generally low because of the high percentage of silt; yields as much as 30 gpm to domestic wells are reported. Under most favorable conditions, these deposits yield as much as 500 gpm. The glaciolacustrine and associated delta deposits occur in nearly all parts of north-central Connecticut and are potential sources of moderate supplies of ground water. They consist of well-sorted sand which generally grades downward into varved clay and silt. The deposits of sand are thic

Water Supply Paper↗
USGS1964

Preliminary results of hydrogeologic investigations in the valley of the Humboldt River near Winnemucca, Nevada

Most of the ground water of economic importance and nearly all the ground water closely associated with the flow o# the Humboldt River in the. 40-mile reach near Winnemucca, Nev., are in unconsolidated sedimentary deposits. These deposits range in age from Pliocene to Recent and range in character from coarse poorly sorted fanglomerate to lacustrine strata of clay, silt, sand, and gravel. The most permeable deposit consists of sand and gravel of Lake Lahontan age--the so-called medial gravel unit--which is underlain and overlain by fairly impermeable silt and clay also of Lake Lahontan age. The ultimate source of nearly all the water in the study area is precpitation within the drainage basin of the Humboldt River. Much of this water reaches the study, area as flow or underflow of the Humboldt River and as underflow from other valleys tributary to the study area. Little if any flow from the tributary streams in the study area usually reaches the Humboldt River. Most of the tributary streamflow within the study area evaporates or is transpired by vegetation, but a part percolates downward through unconsolidated deposits of the alluvial fans flanking the mountains and move downgradient as ground-water underflow toward the Humboldt River. Areas that contribute significant amounts of ground-water underflow to. the valley of the Humboldt River within the study area are (1) the valley of the Humboldt River upstream from the study area, (2) the Pole Creek-Rock Creek area, (3) Paradise Valley, and (4) Grass Valley and the northwestern slope of the Sonoma Range. The total average underflow from these areas in the period 1949-61 was about 14,000-19,000 acre-feet per year. Much of this underflow discharged into the Humboldt River within the study area and constituted a large part of the base flow of the river. Streamflow in the Humboldt River increases substantially in the early spring, principally because of runoff to the river in the reaches upstream from the study area. The resulting increase of the stage of the river causes the river to lose large amounts of water by infiltration to the ground-water reservoir in the study area. In addition, there is much recharge to the ground-water reservoir in the spring and early summer as a result of seepage losses from irrigation ditches and the downward percolation of some of the excess water applied for irrigation. The average net increase of ground water in storage in the deposits beneath and adjacent to the flood plain of the Humboldt River during the spring and early summer is about 10,000 acre-feet.

Nevada↗
USGS1964

Ground-water resources of southern New Castle County, Delaware

Southern New Castle County has a land area of 190 square miles in northcentral Delaware. It is predominantly a rural area with a population of about 9,500 people who are engaged chiefly in agriculture. By and large, the residents are dependent upon ground water as a source of potable water. This investigation was made to provide knowledge of the availability and quality of .the ground-water supply to aid future development. The climate, surface features, and geology of the area are favorable for the occurrence of ground water. Temperatures are generally mild and precipitation is normally abundant and fairly evenly distributed throughout the year. The topography of the area is relatively fiat and, hence, the streams have low gradients. The surface is underlain to a considerable depth by highly permeable unconsolidated sediments that range in age from Early Cretaceous to Recent. Nearly all the subsurface stratigraphic units yield some water to wells, but only four parts or combinations of these units are sufficiently permeable, to yield large supplies. These are, from oldest to youngest, the nonmarine Cretaceous sediments and the Magothy Formation, the Monmouth Group, the Rancocas Formation, and .the surficial terrace and valley-fill deposits. In the northern part of the area the nonmarine Cretaceous sediments and the Magothy Formation can be reached economically by wells. Yields in excess of 300 gpm (gallons per minute) have been obtained from wells screened in this aquifer, but the maximum productivity of the aquifer has not been .tested. The Monmouth Group is used as a source of water in the central part of the area, where some wells yield as much as 125 gpm. The Rancocas Formation is the principal aquifer in the southern part of the area. Yields of 200-400 gpm can be expected from this aquifer, owing to its uniformly coarse texture, particularly in the upper part of the formation. The terrace deposits compose the shallow watertable aquifer throughout the area. In places the water-table aquifer is connected hydraulically to each of .the other three aquifers. The yields of wells tapping this aquifer are generally small, because the saturated thickness of the aquifer is small. The aquifer does provide a convenient and economical source of water for domestic supplies, .and the quality o# the available water supply is generally satisfactory for most purposes. The use of water in the area was estimated to be about 1.77 million gallons per day in 1959. Rural uses amounted to about 75 percent of the total, and municipal and industrial uses accounted for .the remainder. Water for irrigation of crops constituted about half of the water pumped for rural use. The total use of ground water in the area is a mere fraction of the supply available. Each of the four major aquifers is capable of vastly increased production. Future development, however, will be .limited by the changes in the quality of the water resulting from the future pumping regime-and the expanded pattern of development. Salt-water encroachment will become a problem in the eastern part of the area if steps are not taken to avoid it.

Water Supply Paper↗
USGS1963

Ground-water exploration in Al Marj area, Cyrenaica, United Kingdom of Libya

The present report, based largely on fieldwork during 1959-61, describes the results of reconnaissance hydrogeologic studies and exploratory drilling to evaluate the general water-bearing properties of the rocks and the availability of groundwater supplies for irrigation, stock, and village uses in Al Marj area. These studies and the drilling were conducted under the auspices of the U.S. Operations Mission of the International Cooperation Administration. Al Marj area, located in the Province of Cyrenaica on the southern coast of the Mediterranean Sea, contains a land area of about 6,770 square kilometers. Along the Mediterranean shore is a narrow coastal plain that rises evenly to the base of an escarpment that forms the seaward front of an undulating plateau known as. Al Jabal al Akhgiar. The climate is semiarid; seasonal rainfall occurs during the winter months. Owing to orographic effects, the rainfall is somewhat higher in the Jabal than in the coastal plain. The average annual rainfall ranges from about 250 millimeters in the coastal plain to 450 millimeters on the Jabal. All the streams (wadis) of the area are ephemeral and flow only in response to heavy rains of the winter season. From a drainage divide on the Jabal some streams flow north and northwest toward the sea and the others, south and southeast to the interior desert. Solution features, such as limestone sink holes, are common in the coastal plain and a large solution depression occurs near Al Marj. The rocks of A1 Marj area consist predominantly of limestone and some sandstone and shale; they range from Cretaceous to Miocene age. On the coastal plain Miocene limestone is locally mantled by Quaternary alluvial, beach and lagoonal deposits. The Miocene and older beds have a regional southerly dip. These rocks are broken by northeast-trending normal faults in the coastal and inland escarpments. The ground-water reservoir is contained chiefly in fractures, bedding planes, and solution openings in the limestone country rock. The upper limit of this reservoir is marked by a water table which generally lies within 40 meters of the land surface in the coastal plain but is 100 meters or more below the surface of most of the Jabal and the interior desert. The ground-water reservoir is replenished chiefly by infiltration from surface-water runoff in wadis and to less extent by direct infiltration of rainfall. Ground water moves north and northwest toward the Mediterranean Sea and south toward the interior desert from a ground-water divide near the crest of A1 Jabal al Akhgiar. Discharge of ground water takes place by submarine outflow, spring flow, evapotranspiration, and withdrawals from wells. Wells, springs, and cisterns furnish almost all water supplies for municipal, village, stock and irrigation purposes. Bengasi, A1 Marj, and A1 Abyar are the only centers of population with municipal distribution systems. Drafts from individual dug wells used for irrigation in the coastal plain generally are no more than 10 to 15 cubic meters per day. In the Jabal and the interior desert drafts from individual stock and village wells are generally less than 10 cubic meters per day and from most wells only a few thousand liters per day. Some 21 test wells were put down during the present investigation to depths ranging from 30 to 309 meters. The yields obtained by test pump and bailer ranged from 45 to 0.6 cubic meters per hour. With few exceptions, well yields sufficient for stock and village requirements were obtained. Well yields sufficient for irrigation even on a moderate scale, however, are not everywhere available. In the Jabal and the interior desert the ground water is generally of good to fair chemical quality and suitable for most purposes. In the coastal plain, however, the ground water is in places moderately to highly mineralized, and consequently for irrigation use it must be applied to the land under optimum crop soil, and drainage conditions.

Water Supply Paper↗
USGS1964

Ground water in the Sirte area, Tripolitania, United Kingdom of Libya

The present study of the ground-water conditions in the Sirte area was made during December 1961 and March-April 1962 at the request of officials of the Government of Libya. Particular attention was given to the potential of the fresh-water aquifer near Qasr Bu Itadi as a source of water for Sirte. The Sirte area lies on the southern coast of the Mediterranean Sea about 450 kilometers east-southeast of Tripoli, cocapital of Libya. Although the area receives some winter precipitation, the climate is arid. The surface rocks of the area are chiefly Miocene limestone containing marl, clay, and some sandstone, though Quaternary deposits occur along the wadis and mantle the Miocene rocks in the coastal plain. Fresh ground water occurs locally in Recent sand dunes near Zaafran and in Miocene limestone near Qasr Bu Hadi, south of a probable fault. Elsewhere in the Sirte area, ground water occurs generally in Tertiary rocks but contains 3,000 or more parts per million of dissolved solids. To establish the hydraulic characteristics of the fresh-water aquifer in the Qasr Bu Itadi area, two test wells were drilled and a controlled pumping test was made. The coefficient of transmissibility was found to be about 25,000 gallons per day per foot (13.68 cubic meters per hour per meter), and the coefficient of storage, about 0.00055. The pumping test also established the presence of two barrier-type hydraulic boundaries for the aquifer, one about 250 meters westward and another about 535 meters northward from well 9a. The first boundary is probably the small anticline on which stands the fort of Qasr Bu Itadi; the second boundary is probably a northwest trending fault. Using the transmissibility and storage coefficients derived from the pumping test, the writer concludes that (1) the total draft from the fresh-water aquifer should not exceed 13.5 cubic meters per hour and (2) production wells should be at least 3 kilometers south of well 9a.

Water Supply Paper↗
USGS1964

Ground-water provinces of southern Rhodesia

Ground-water development, utilization, and occurrence in nine ground-water provinces of Southern Rhodesia are summarized in this report. Water obtained from drilled wells for domestic and stock use has played an important part in the social and economic development of Southern Rhodesia from the beginnings of European settlement to the present. Most of the wells obtain water from fractures and weathered zones in crystalline rocks, before recently, there has been an interest in the possibility of obtaining water for irrigation from wells. Studies of the authors indicate that quantities of water sufficient for irrigation can be obtained from alluvial sediments in the S'abi Valley, from Kalahari sands in the western part of the country, are perhaps from aquifers in other areas. The ground-water provinces fall into two groups--those in the crystalline rocks and those in the noncrystalline rocks. Historically, the wells in crystalline rocks, especially the Gold belts province and the Intrusive granites province, have played a major role in supplying water for the needs of man. These provinces, together with two other less important crystalline rock provinces, form the broad arch which constitutes the central core of the country. The noncrystalline rocks overlie and flank the crystalline rocks to the southeast, northwest, and north. The noncrystalline rock provinces, especially the Alluvium-Kalahari province, contain the most productive or potentially productive ground-water reservoirs in Southern Rhodesia and offer promise of supplying water for irrigation and for other purposes.

Water Supply Paper↗
USGS1968

Ground-water hydrology of the Chad Basin in Bornu and Dikwa Emirates, northeastern Nigeria, with special emphasis on the flow life of the artesian system

Bornu and Dikwa Emirates lie in the Nigerian sector of the Chad Basin, a vast region of interior drainage encompassing about 600,000 square miles of north-central Africa. The report area includes about 25,000 square miles of the basin that lie in Nigeria. Most of the area is a featureless plain that slopes gently northeast and east from the uplands of central Nigeria towards Lake Chad. On its eastern side the lake has one surface outlet which overflows only during exceptionally high stages of the lake. This outlet spills into the channel of Bahr al Ghazal, which in turn drains into the Bod616 depression. Because the lake is shallow, the shoreline fluctuates markedly with high and low stages corresponding to the wet and dry seasons. The semiarid climate of Bornu and Dikwa Emirates is characterized by a long dry season and a short wet season that correspond to seasonal winds. Annual rainfall ranges from 15 inches in the northern part of the area to 32 inches in the southern. The Chad Basin in Dikwa and Bornu Emirates is underlain by interbedded sand and clay, collectively termed the Chad Formation. These alluvial and lactustrine sediments were deposited in or near Lake Chad whet it occupied a much greater area during Pliocene and Pleistocene time. The Chad Formation has a very slight primary dip in the direction of Lake Chad and conforms to the gentle slope of land surface. The known thickness of the formation ranges from a few feet where it overlies bedrock on the periphery of the basin to at least 1,800 feet at Maiduguri; however, its total thickness probably exceeds 2,000 feet in the central part of the basin. Three water-bearing units termed upper, middle, and lower zones occur within the Chad Formation. The upper zone yields water to numerous dug wells throughout the rural areas and also is .the major source of the Maiduguri municipal water .supply. The middle zone yields water from flowing artesian boreholes that have heads ranging from a few feet to 70 feet above land surface throughout a 13,000 square-mile area of the basin in Nigeria. The lower zone also yields water from flowing boreholes ; however, its areal extent has not been proved beyond the environs of Maiduguri. The present investigation is concerned primarily with the middle zone, which is the source of water for some 190 flowing boreholes used as little-watering points in the Nigerian sector of the Chad Basin. The thickness of loads of waterbearing sand in the middle zone ranges from less than 1 foot to 200 feet, and the artesian head ranges from land surface at Maiduguri to 70 feet above land surface at Lake Chad. The depth to the top of the middle zone in the area of flowing boreholes ranges from 500 to 1,250 feet below land surface. The waterbearing properties of the middle zone differ greatly from place to place. Also, the yields of individual flowing boreholes generally range from 50 to 20,000 imperial gallons per hour (gph). On the basis of water availability, the middle zone can be divided as follows : Areas of high-, moderate-, and low-yield artesian aquifer ; areas of low- and moderate-yield subartesian aquifer ; and an area where the yields from boreholes are insignificant or the aquifer is missing. Recommended maximum rates of long-term withdrawal from individual boreholes for the three artesian areas range from 100 to 5,000 gph with boreholes spaced 5 to 10 miles apart. By limiting flows to the recommended maximum rates, the boreholes should continue to flow for at least 30 years. The present average use per borehole (265 gph in 1965) is considerably less than the recommended maximum rates. Recharge to the upper zone occurs in significant but as yet unmeasured quantities, mostly in the vicinity of the major streams. Apparently, however, no significant amount of recharge reaches the middle zone from the Upper zone. Although the middle zone is, in effect, being 'mined' by existing flowing wells, the present (1965) rate of withdrawal i

Water Supply Paper↗
USGS1968

Ground-water geology of Kordofan Province, Sudan

For much of Kordofan Province, surface-water supplies collected and stored in hafirs, fulas, and tebeldi trees are almost completely appropriated for present needs, and water from wells must serve as the base for future economic and cultural development. This report describes the results of a reconnaissance hydrogeologic investigation of the Province and the nature and distribution of the ground-water resources with respect to their availability for development. Kordofan Province, in central Sudan, lies within the White Nile-Nile River drainage basin. The land surface is largely a plain of low relief; jebels (hills) occur sporadically, and sandy soils are common in most areas except in the south where clayey soils predominate. Seasonal rainfall, ranging from less than 100 millimeters in the north to about 800 millimeters in the south, occurs almost entirely during the summer months, but little runoff ever reaches the Nile or White Nile Rivers. The rocks beneath the surficial depsits (Pleistocene to Recent) in the Province comprise the basement complex (Precambrian), Nawa Series (upper Paleozoic), Nubian Series (Mesozoic), laterite (lower to middle Tertiary), and the Umm Ruwaba Series (Pliocene to Pleistocene). Perennial ground-water supplies in the Province are found chiefly in five hydrologic units, each having distinct geologic or hydrologic characteristics. These units occur in Nubian or Umm Ruwaba strata or both, and the sandstone and conglomerate beds form the :principal aquifers. The water is generally under slight artesian head, and the upper surface of the zone of saturation ranges from about 50 meters to 160 meters below land surface. The surficial deposits and basement rocks are generally poor sources of ground water in most of the Province. Supplies from such sources are commonly temporary and may dissipate entirely during the dry season. Locally, however, perennial supplies are obtained from the surficial deposits and from the basement rocks. Generally, water from Nubian aquifers is satisfactory for most uses and is of better quality than that obtained from Umm Ruwaba aquifers. The relatively high mineralization of water from the Umm Ruwaba, especially in the eastern part of the Province, makes the water unsuitable for many municipal ad industrial uses. The water is generally usable, however, for domestic and livestock purposes. Some 175 drilled wells located at 75 water yards yield an average, of about 1,000 imperial gallons .per hour per well from Nubian or Umm Ruwaba. aquifers. Generally the water yards provide sufficient water for minimum domestic and livestock requirements throughout the year. Commonly, however, the water yards are widely separated and, hence, not always properly spaced for good range management or for serving the needs of the dispersed rural population. In 1962, withdrawals from Nubian and Umm Ruwaba aquifers in the Province were approximately 600 million gallons annually. This rate of draft: could probably be continued almost indefinitely without significant depletion of the water supply. Nubian and Umm Ruwaba aquifers in the southwestern part of Kordofan offer excellent potential for future development. Nubian aquifers in northern Kordofan need extensive exploration by test drilling before their economic potential can be properly evaluated.

Water Supply Paper↗