RECHARGE ESTIMATES USING A GEOMORPHIC/DISTRIBUTED-PARAMETER SIMULATION APPROACH,AMARGOSA RWER BASIN1

ABSTRACT: Average-annual volumes of runoff, evapotranspiration, channel loss, upland (interchannel) recharge, and total recharge were estimated for watersheds of 53 channel sites in the Amargosa River basin above Shoshone, California. Estimates were based on a water-balance approach combining field techniques for determining streamflow with distributed-parameter simulation models to calculate transmission losses of ephemeral streamflow and upland recharge resulting from high-magnitude, low-frequency precipitation events. Application of the water-balance models to the Amargosa River basin, Nevada and California, including part of the Nevada Test Site, suggests that about 20.5 million cubic meters of water recharges the ground-water reservoir above Shoshone annually. About 1.6 percent of precipitation becomes recharge basinwide. About 90 percent of the recharge is by transmission loss in channels, and the remainder occurs when infrequent storms yield sufficient precipitation that soil water percolates beyond the rooting zone and reaches the zone of saturation from interchannel areas. Highest rates of recharge are in headwaters of the Amargosa River and Fortymile Wash; the least recharge occurs in areas of relatively low precipitation in the lowermost Amargosa River watershed.     

USE OF SOIL MOISTURE PROBES TO ESTIMATE GROUND WATER RECHARGE AT AN OIL SPILL SITE1

Soil moisture data collected using an automated data logging system were used to estimate ground water recharge at a crude oil spill research site near Bemidji, Minnesota. Three different soil moisture probes were tested in the laboratory as well as the field conditions of limited power supply and extreme weather typical of northern Minnesota: a self‐contained reflectometer probe, and two time domain reflectometry (TDR) probes, 30 and 50 cm long. Recharge was estimated using an unsaturated zone water balance method. Recharge estimates for 1999 using the laboratory calibrations were 13 to 30 percent greater than estimates based on the factory calibrations. Recharge indicated by the self‐contained probes was 170 percent to 210 percent greater than the estimates for the TDR probes regardless of calibration method. Results indicate that the anomalously large recharge estimates for the self‐contained probes are not the result of inaccurate measurements of volumetric moisture content, but result from the presence of crude oil, or borehole leakage. Of the probes tested, the 50 cm long TDR probe yielded recharge estimates that compared most favorably to estimates based on a method utilizing water table fluctuations. Recharge rates for this probe represented 24 to 27 percent of 1999 precipitation. Recharge based on the 30 cm long horizontal TDR probes was 29 to 37 percent of 1999 precipitation. By comparison, recharge based on the water table fluctuation method represented about 29 percent of precipitation.     

Influence of compost amendment rate and level of compaction on the hydraulic functioning of soils

There has been widespread interest in using compost to improve the hydrologic functions of degraded soils at construction sites for reducing runoff and increasing infiltration. The objective of this study was to determine the effects of compost amendment rate on saturated hydraulic conductivity (K_s) and water retention in order to identify target compost rates for enhancing soil hydrologic functions. Samples were prepared with three soil textures (sandy loam, silt loam, and sandy clay loam), amended with compost at 0%, 10%, 20%, 30%, 40%, and 50%. All soils were tested at a porosity of 0.5 m³/m³, and the sandy loam was further tested at high (0.55 m³/m³) and low (0.4 m³/m³) porosities. The K_s and water retention data were then used to model infiltration with HYDRUS-1D. With increasing compost amendment rate, K_s and water retention of the mixtures generally increased at the medium porosity level, with more compost needed in heavier soils. As porosity decreased in the sandy loam soil, the amount of compost needed to improve K_s rose from 20% to 50%. Water distribution in pore fractions (gravitational, plant-available, and unavailable water) depended on texture, with only the highest compost rates increasing plant-available water in one soil. Results suggest soil texture should be taken into consideration when choosing a compost rate in order to achieve soil improvement goals. Hydrologic benefits may be limited even at a high rate of compost amendment if soil is compacted.     

EFFECTS OF SIMULATED CANOPY COVER AND ANIMAL DISTURBANCES ON RILL AND INTERRILL EROSION1

ABSTRACT: A rainfall simulator was used on runoff plots to study the effects of simulated canopy cover, trampling disturbance, and soil type on nil and interrill erosion. Sandy loam soil was more erodible than clay loam soil. Furthermore, the simulated canopy cover signffi-Soilfactorsrelatedtonil cantly influenced nil and interrill erosion. The effect of trampling on rill and interrill erosion varied with soil type (clay loam versus sandy loam) and erosion type (nh versus interrill erosion). On large plots, where both nil and internill erosion were involved, 30 percent trampling significantly increased soil loss. However, on small plots, 30 percent trampling significantly reduced interrill erosion.     

MODELING WATER BALANCE WITH THE ERHYM MODEL ON SOUTH TEXAS RANGELANDS1

ABSTRACT: Understanding the hydrologic processes of rangeland plant communities is essential to determine if water augmentation through shrub management is feasible. Vegetation manipulation studies are costly, difficult to accurately replicate, and often require more than 10 years to determine treatment effect on the water budget. If properly applied, hydrologic simulation models are an attractive alternative for assessing vegetation manipulation practices. The ERHYM-II model was evaluated to determine if it was capable of simulating the water balance for honey mesquite shrub clusters, grass interspaces, and bare soil in south Texas. The simulated water budget was within 2 percent of the measured evapotranspiration for the shrub clusters and grass interspaces. The model underestimated the number of runoff events and overestimated runoff volume for the grass interspace and shrub clusters. Simulated runoff was overestimated by approximately twofold for the grass interspace and threefold for the shrub clusters. Although simulated runoff was substantially overestimated, observed and simulated runoff only accounted for 3 to 6 percent of annual rainfall for the grass and shrub dominated areas, respectively. Simulated evapotranspiration was underestimated by 18 percent and soil water content was overestimated by 82 percent for the bare soil. The model underestimated evapotranspiration for the bare soil as a result of restricting evaporative losses to the first soil layer. Based on our analysis, the ERHYM-II model has the potential for simulating the annual water balance for semiarid rangeland plant communities where runoff and deep drainage are limited components of the water balance.     

DRAINAGE GENERATION AND WATER USE IN THE EVERGLADES AGRICULTURAL AREA BASIN1

ABSTRACT: The Everglades Agricultural Area (EAA) covers 2,850 km² in area and is characterized by high water table and organic soil. The area is actively irrigated and drained as a function of weather conditions and crop status. Anthropogenic activities in the basin have resulted in nutrient-enriched drainage water that is discharged to Lake Okeechobee and the Everglades ecosystem. Water quantity and quality issues of the basin have become of increasing interest at local, state, and federal levels, so legislative and regulatory measures have been taken to improve water quality in discharges from the basin. In this study, simulation of hydrologic conditions and soil moisture were conducted using 100 years of daily synthetic rainfall data. From the simulations, the statistical distribution of half-month drainage discharge and supplemental water use in the basin was developed. The mean annual drainage/runoff was 49 cm, the mean supplemental water was 30 cm, and the mean annual a real rainfall was 122 cm. On the average, drainage exceeded supplemental water use in the months of June to September while from December to March drainage and supplemental water use were equivalent. Supplemental water use exceeded drainage in the months of October, November, April, and May. High drainage occurred in June and September; smallest drainage was in February. On the average, the highest supplemental water use occurred in May and November. The 10-year return period of annual drainage during wet and dry cycles were 60 cm and 38 cm per year, respectively. The semi-monthly drainage coefficient of variation (cv) is above 100 percent for the period from the second half of October to end of April. The cv is lower than 100 percent for the remaining season (wet season). The purpose of this paper is to present the magnitude, temporal, and frequency distribution of drainage runoff generation and supplemental water use in the EAA basin. Information on statistics of drainage will contribute to the optimization of the design and operation of drainage water treatment systems.     

ACCUMULATION OF AS,NI, CU,AND PB IN RETENTION AND RECHARGE BASINS SOILS FROM URBAN RUNOFF1

ABSTRACT: The accumulation of arsenic, nickel, copper, and lead in the soil profile was determined beneath five urban storm-water retention/recharge basins used by the Fresno Metropolitan Flood Control District, California. Soils were sampled from the surface to the first zone of saturation and compared with soils from an adjacent un-contaminated control site. These elements were found to be accumulating in the first few centimeters of basin soil and are important to the effectiveness of a specific best management practice, i.e., the retention and recharge of urban storm water. Study basins in use since 1962, 1965, and 1969 had lead contents in the 0–2 cm soil depth interval‘of 570, 670, and 1400 mg Pb/kg soil, respectively. The median indigenous soil lead concentration was 4.6 mg/kg soil. The practice of removing excess flood runoff water from two basins by pumping apparently is a factor in reducing the accumulation rate of these elements in the surface soils of the basins.     

ARTIFICIAL GROUND WATER RECHARGE BY FLOODING DURING GRAPEVINE DORMANCY1

ABSTRACT: The potential for artificial ground water recharge by continuous flooding of dormant grapevines was evaluated in the San Joaquin Valley of California using the cultivar Thompson Seedless. The study was started in 1982 and was completed in 1985 after three complete flooding cycles during dormancy. An average daily rate of recharge of 80 mm/thy for a 32-day period each year was achieved through a clay loam soil. There were no adverse effects on the grapevines and yields in the flooded plots in any of the growing seasons following recharge periods. Yields were higher in the recharge plots than in the control plots in the last year of the study. We conclude that artificial ground water recharge by continuous flooding during grapevine dormancy is a viable recharge method.     

WATER QUALITY BENEATH URBAN RUNOFF WATER MANAGEMENT BASINS1

ABSTRACT: The chemical impact of urban runoff water on water quality beneath five retention/recharge basins was investigated as part of the US EPA's Nationwide Urban Runoff Program in Fresno, California. Soil water percolating through alluvium soils and the ground water at the top of the water table were sampled with ceramic/Teflon vacuum water extractors at depths up to 26 m during the two-year investigation. Inorganic and organic pollutants are present in the runoff water delivered to the basins. No significant contamination of percolating soil water or ground water underlying any of the five retention/recharge basins has occurred for constituents monitored in the study. The oldest basins was constructed in 1962. The concentration of selected trace elements in the ground water samples was similar to the levels reported in the regional ground water. None of the pesticides or other organic priority pollutants, for which water samples were analyzed, was s̊ detected except diazinon which was found in trace amounts (0.3 μg/L or less) in only three soil water samples. These results are important to the continued conservation of storm water and the development of a best management practice for storm-water management using retention/recharge basins in a semi-arid climate.     

WATER BUDGET ANALYSIS FOR THE EVERGLADES AGRICULTURAL AREA DRAINAGE BASIN1

ABSTRACT: Water budget studies are essential for water resources and environmental management. In this study, a water budget analysis is presented for the Everglades Agricultural Area (EAA) in South Florida for the period from 1973 to 1991. The EAA is a highly productive irrigation/drainage basin that has a high water table and organic soils. Water quality problems are associated with the drainage discharge from the basin. During dry periods, supplemental water is used for irrigation and in rainy periods excess water with relatively higher phosphorus content is pumped out of the basin to Lake Okeechobee and the Everglades ecosystem. Elevated concentrations of phosphorus in the runoff/drainage that is discharged from the EAA basin have created water quality problems. The mean surface water inflow to the basin was 63,990 ha-m, and the outflow was 131,447 ha-m per year. On the average, supplemental surface water use was 47,411 ha-m, and runoff/drainage was 114,816 ha-m per year. The mean annual basin rainfall was 120.9 cm. A general trend in the decline of the wet season rainfall is observed.     

LEAKY ACRES RECHARGE FACILITY: A TEN-YEAR EVALUATION1

From 1971-1980, studies were conducted at Fresno, California, to identify and quantify, where possible, the soil and water chemistry, subsurface geologic, hydrologic, biologic, and operational factors that determine the long term (10-year) effectiveness of basin type artificial ground water recharge through alluvial soils. This paper updates previous findings and refers to publications that describe the geology beneath the basins and regional geology that determine the transmission and storage properties for local ground water management and chemical quality enhancement. High quality irrigation water from the Kings River was used for recharge. Construction and land costs for the present expanded facility 83 ha (205.2 ac) using three parcels of land were $1,457,100. The nine-year annual mean costs for only canal water, maintenance, and operation were $110.42/ha·m ($13.62/ac·ft) based on an average recharge rate of 1338 ha·m/yr (10,848 ac·ft/yr) at 86 percent facility efficiency. The measured end of season recharge rate averaged 14.97 ± 0.24 cm/day. The 10-year mean actual recharge rate based on actual water delivered, total ponded area, and total days of recharge was 12.1 cm/day.     

SPATIAL VARIABILITY IN WATER‐BALANCE MODEL PERFORMANCE IN THE CONTERMINOUS UNITED STATES1

ABSTRACT: A monthly water‐balance (WB) model was tested in 44 river basins from diverse physiographic and climatic regions across the conterminous United States (U.S.). The WB model includes the concepts of climatic water supply and climatic water demand, seasonality in climatic water supply and demand, and soil‐moisture storage. Exhaustive search techniques were employed to determine the optimal set of precipitation and temperature stations, and the optimal set of WB model parameters to use for each basin. It was found that the WB model worked best for basins with: (1) a mean elevation less than 450 meters or greater than 2000 meters, and/or (2) monthly runoff that is greater than 5 millimeters (mm) more than 80 percent of the time. In a separate analysis, a multiple linear regression (MLR) was computed using the adjusted R‐square values obtained by comparing measured and estimated monthly runoff of the original 44 river basins as the dependent variable, and combinations of various independent variables [streamflow gauge latitude, longitude, and elevation; basin area, the long‐term mean and standard deviation of annual precipitation; temperature and runoff; and low‐flow statistics (i.e., the percentage of months with monthly runoff that is less than 5 mm)]. Results from the MLR study showed that the reliability of a WB model for application in a specific region can be estimated from mean basin elevation and the percentage of months with gauged runoff less than 5 mm. The MLR equations were subsequently used to estimate adjusted R‐square values for 1,646 gauging stations across the conterminous U.S. Results of this study indicate that WB models can be used reliably to estimate monthly runoff in the eastern U.S., mountainous areas of the western U.S., and the Pacific Northwest. Applications of monthly WB models in the central U.S. can lead to uncertain estimates of runoff.     

Slope and pig slurry rate may increase the transfer of chemical elements by surface water runoff

There is a need to evaluate the interference of pig slurry rate and the terrain slope in the chemical elements losses from the soil. This work aimed to quantify water and chemical element losses by surface runoff due to terrain slope and pig slurry rate (PS) in two soils with contrasting textures. Two trials were evaluated in 2018 and 2019 in Cambisol and Nitisol. Rates of 0, 22.5, 45, and 90 m³ ha⁻¹ yr⁻¹ of PS were applied superficially in sites with slopes ranging from 10% to 35%. Perennial forage grass Tifton 85 (Cynodon dactylon) was grown as summer crop and ryegrass (Lolium multiflorum) was sown in the cold seasons in a field environment. Were determined the runoff, the volume of water, and chemical elements (Al, Ca, P, Mg, Cd, Cr, Cu, Mn, Fe, Pb, and Zn) lost by the surface runoff after natural rainfall. Increasing land slope elevated water losses substantially, on average 23.4 times in Cambisol and 10.8 times in Nitisol. This increase resulted in average increases of 27.6 and 12.4 times in the losses of the chemical elements analyzed for Cambisol and Nitisol, respectively. There was a reduction in water losses by surface runoff due to increased PS rates applied in both sites. The increased PS rate affected the losses of Cr and Cu in Cambisol and P, Mg, Cd, and Cu in Nitisol. The clayey soil potentiated the water and chemical elements losses by surface runoff in relation to the soil with lower clay content. Regardless of the soil, water and chemical element losses are maximized at higher slopes.     

A CASE STUDY OF SHALLOW FLOW PATHS IN A STEEP ZERO-ORDER BASIN1

ABSTRACT: Soil water potentials, slope throughflow, runoff chemistry, and isotopic composition were monitored in a 97 m² zero-order basin within the Maimai 8 watershed on the South Island of New Zealand, for a natural rain storm and two artificial water applications. Contrary to results previously reported for other portions of the Maimai catchment, much of the runoff occurred as a shallow subsurface organic layer flow. For the 47 mm natural rain event, pre-storm soil matric potential ranged from ?60 to ?150 cm H₂O. No saturation was produced within the profile, and the majority of storm runoff emanated from flow within the organic horizon perched on the mineral soil surface. Hillslope applications corroborated this interpretation by showing >90 percent new water flushing with negligible mineral soil moisture response. Although the mechanisms cited in the text are not representative of the entire catchment, the study demonstrates: (1) the value of a combined physical-chemical-isotopic approach in quantifying slope processes, and (2) the heterogeneous nature and diversity of slope runoff pathways in a relatively homogeneous catchment.     

UTILIZING INDUCED RECHARGE FOR REGIONAL AQUIFER MANAGEMENT1

ABSTRACT: The deep aquifers of the Portland Basin are used as a regional water supply by at least six municipalities in Oregon and Washington. Maximum continuous use of the aquifers in 1998 was 13 mgd and peak emergency use was 55 mgd. Continuous use of the deep aquifers at a rate of 55 mgd has been proposed and inchoate water rights have been reserved for expansion of pumping to 121 mgd. A study was completed, using a calibrated ground water flow model, to evaluate the role of induced recharge from the Columbia River in mitigating aquifer drawdown from continuous‐use and expanded pumping scenarios in the center and eastern areas of the basin. The absolute average residual was less than 3.6 feet for steady‐state model calibrations, and less than 8.0 feet for transient calibration to a 42 mgd pumping event in 1987 with 170 feet of drawdown. Continuous use of the aquifers at a rate of 55 mgd is predicted to increase drawdown to 210 feet. Expansion of pumping to 121 mgd in the center basin is predicted to cause 400 feet of drawdown. However, expansion of pumping in the east basin is predicted to result in only 220 feet of drawdown because of induced recharge from the Columbia River.     

EFFECTS OF A NORTH CENTRAL WASHINGTON WILDFIRE ON RUNOFF AND SEDIMENT PRODUCTION1

ABSTRACT: Runoff was measured from a 564-ha catchment located on the Entiat Experimental Forest for nine years before a severe wild-fire in 1970 destroyed the mixed conifer vegetation. Runoff records from the Chelan River (2 393 km²) were used as control data for determining changes in water yield during the seven years following the fire. The first post-fire year was a period of transition in which the soil profile retained more water than in previous years and measured runoff was 8.9 cm greater than the predicted value based on pre-fire conditions. Runoff from the burned catchment during subsequent years was much greater than measured values before the fire. Measured minus predicted runoff, based on the pre-fire calibration equation, varied from 10.7 cm during the dry year of 1977 to 47.2 cm during the abnormally wet year of 1972. Flow duration curves indicated that runoff at each percent value after the fire was at least double the comparable pre-fire value. Sediment production increased dramatically after the fire because of increased flow rates, increased overland flow caused by reduced infiltration capacity, and mass soil movement. Sediment yield is beginning to decrease as stream channels become stabilized and vegetation on upper slopes improves infiltration capacity.     

GROUNDWATER MANAGEMENT ON THE TEXAS HIGH PLAINS1

ABSTRACT The effects of major water management practices on the pumping requirement from the Ogallala aquifer are discussed. Demand on the aquifer may be reduced as much as 15 percent by recycling irrigation runoff, 25 percent by recycling irrigation runoff and irrigating with water from playas, and 29 percent by recycling irrigation water in combination with irrigation from playas and artificial recharge of playa water to the aquifer. Other practices that can result in more efficient use of precipitation and groundwater are limited irrigation, land forming, soil profile modification, and improved irrigation systems, thereby reducing the pumping demand on the Ogallala. Additional water supplies can possibly be obtained by water harvesting, weather modification, and water importation. Conclusions reached were that the overdraft on the aquifer can be reduced by the application of sound water management practices on an area-wide basis.     

Determining long-term (decadal) deep drainage rate using multiple tracers

The deep drainage rate is a critical hydrological parameter in understanding contamination mechanisms of soil and groundwater. Little research has been conducted on the temporal variations in deep drainage rate during the last century. The objective of this study was to determine the long-term deep drainage rate on a cultivated loamy soil in the Canadian Prairies. Three tracers were used: KCl applied in 1971, fallout tritium in 1963, and NO3* released during the initial cultivation of the field (1923). Two soil cores to a depth of 3.6 m were taken along a flat portion of the field, and soil Cl(-), 3H, and NO3* concentrations were measured as a function of depth. An additional four cores were taken for soil water content measurements between 2000 and 2003. Distinct peaks in the depth distribution of these three tracers were located at 1.27 m for Cl(-), 1.31 m for 3H, and 1.52 m for NO3*, 32, 40, and 80 yr after the application of Cl(-), 3H, and NO3*, respectively. The average deep drainage rates, calculated as the product of the estimated tracer velocity and volumetric soil water content below the active root zone, were 2.0 mm yr(-1) from the Cl(-) tracer, 2.2 mm yr(-1) from 3H, and 2.5 mm yr(-1) from the NO3* tracer. Therefore, there was little temporal variability in the groundwater recharge over the eight decades that the field has been cultivated. The recharge rates are less than 1% of the mean annual precipitation (333 mm).     

TEMPERATURE EFFECTS ON GREAT LAKES WATER BALANCE STUDIES1

ABSTRACT. Beginning of month water temperature profiles are estimated for each lake. These water temperature profiles along with surface water temperatures are used to determine the effects of thermal expansion and contraction of water on the net basin supply values obtained from water balance studies using end of month lake levels. It is demonstrated that net basin supply values (equivalent to precipitation on the lake minus the evaporation from the lake plus the runoff into the lake) obtained from water balance studies without accounting for the thermal expansion and contraction of water may be in error by as much as 100 percent during some months for each lake.     

SIMULATING THE EFFECTS OF REDUCED PRECIPITATION ON GROUND WATER AND STREAMFLOW IN THE NEBRASKA SAND HILLS1

ABSTRACT: The Nebraska Sand Hills have a unique hydrologic system with very little runoff and thick aquifers that constantly supply water to rivers, lakes, and wetlands. A ground water flow model was developed to determine the interactions between ground water and streamflow and to simulate the changes in ground water systems by reduced precipitation. The numerical modeling method includes a water balance model for the vadose zone and MOD‐FLOW for the saturated zone. The modeling results indicated that, between 1979 and 1990, 13 percent of the annual precipitation recharged to the aquifer and annual ground water loss by evapotranspiration (ET) was only about one‐fourth of this recharge. Ground water discharge to rivers accounts for about 96 percent of the streamflow in the Dismal and Middle Loup rivers. When precipitation decreased by half the average amount of the 1979 to 1990 period, the average decline of water table over the study area was 0.89 m, and the streamflow was about 87 percent of the present rate. This decline of the water table results in significant reductions in ET directly from ground water and so a significant portion of the streamflow is maintained by capture of the salvaged ET.