THE ECONOMIC VALUE OF GROUND WATER RECHARGE FOR IRRIGATION USE1

ABSTRACT: Artificial recharge as a means of augmenting water sup plies for irrigation is a management alternative which policy makers in ground water decline areas are beginning to consider seriously. A conceptual model is developed to evaluate the economic benefits from ground water recharge under conditions where the major water use is irrigation. The methodology presented separates recharge benefits into two components: pumping cost savings and aquifer extension benefits. This model is then applied to a Nebraska case to approximate the value of recharge benefits as a function of aquifer response. discount rate, and commodity prices. It was found that recharge benefits vary from less than $2 to over $6 an acre foot recharged.     

A DIGITAL MODEL APPLIED TO GROUND WATER RECHARGE AND MANAGEMENT1

ABSTRACT: Under Colorado's appropriative water right system, withdrawals by junior ground water rights must be curtailed to protect senior surface water appropriators sharing the same river system unless the ground water users replace the amount of their injury to the river under an approved plan for augmentation. Compensation of such injury with surface water may not only be expensive but unreliable in dry years. As an alternative, the curtailment of pumping may be obviated by recharging unused surface water into the aquifer when available and withdrawing it when needed. In order to manage such an operation, a practical tool is required to accurately determine that portion of the recharge water that does not return to the river before pumping for irrigation. A digital model was used for this purpose in a demonstration recharge project located in the South Platte River basin in northeastern Colorado. This paper summarizes the experiences gained from this project, the results of the digital model, the economic value of recharge, and the feasibility of the operation. It was determined through the use of the digital model that, with the given conditions in the area, 77 percent of the recharged water remained available for pumping. Economic analyses showed that water could be recharged inexpensively averaging about two dollars per acre foot.     

Analytical Solutions to the Linearized Boussinesq Equation for Assessing the Effects of Recharge on Aquifer Discharge1

Boggs, Kevin G., Robert W. Van Kirk, Gary S. Johnson, Jerry P. Fairley, and P. Steve Porter, 2010. Analytical Solutions to the Linearized Boussinesq Equation for Assessing the Effects of Recharge on Aquifer Discharge. Journal of the American Water Resources Association (JAWRA) 46(6):1116–1132. DOI: 10.1111/j.1752-1688.2010.00479.x Abstract: There is a need to develop a general understanding of how variations in aquifer recharge are reflected in discharge. Analytical solutions to the linearized Boussinesq equation governing flow in an unconfined aquifer provide a unified mathematical framework to quantify relationships among lag time, attenuation and distance between aquifer recharge and discharge and the effect of an up-gradient no-flow boundary. We applied this framework to three types of recharge: (1) instantaneous, (2) periodic, and (3) constant rate for a finite duration. When the temporal scale of recharge exceeds the diffusive aquifer time scale, recharge will be reflected in discharge quickly and with little attenuation. When aquifer time scale is large, most recharge events are shorter in scale than that of the aquifer, resulting in large attenuation. Attenuation is more sensitive to boundary effects than lag time, and boundary effects increase as recharge time scale increases. Boundary effects can often be ignored when the recharge source is farther than 1/3 of the domain length away from the no-flow boundary. We illustrate analytical results with application to the economically critical Eastern Snake River Plain Aquifer in Idaho. In this aquifer, detectable annual and decadal cycles in discharge can result from recharge no farther than 20 and 60 km away from the discharge point, respectively. The effects of more distant, long-term recharge can be detected only after a time lag of several decades.     

STABLE ISOTOPE CHARACTERIZATION OF THE IMPACTS OF ARTIFICIAL GROUND WATER RECHARGE1

ABSTRACT: Stable isotopes of deuterium and oxygen-18 of surface and ground water, together with anion concentrations and hydraulic gradients, were used to interpret mixing and flow in ground water impacted by artificial recharge. The surface water fraction (SWF), the percentage of surface water in the aquifer impacted via recharge, was estimated at different locations and depths using measured deuterium/hydrogen (DIH) ratios during the 1992, 1993, and 1994 recharge seasons. Recharged surface water completely displaced the ground water beneath the recharge basins from the regional water table at 7.60 m to 12.16 m below the land surface. Mixing occurred beneath the recharge structures in the lower portions of the aquifer (>12.16 m). Approximately 12 m down-gradient from the recharge basin, the deeper zone (19.15 m depth) of the primary aquifer was displaced completely by recharged surface water within 193, 45, and 55 days in 1992, 1993, and 1994, respectively. At the end of the third recharge season, recharged surface water represented ～50 percent of the water in the deeper zone of the primary aquifer ～1000 m downgradient from the recharge basin. A classic asymmetrical distribution of recharged surface water resulted from the recharge induced horizontal and vertical hydraulic gradients. The distribution and breakthrough times of recharged surface water obtained with stable isotopes concurred with those of major anions and bromide in a tracer test conducted during the 1995 recharge season. This stable isotope procedure effectively quantified mixing between surface and ground water.     

REGIONAL SCALE MODELING OF SURFACE AND GROUND WATER INTERACTION IN THE SNAKE RIVER BASIN1

ABSTRACT: Changes in irrigation and land use may impact discharge of the Snake River Plain aquifer, which is a major contributor to flow of the Snake River in southern Idaho. The Snake River Basin planning and management model (SRBM) has been expanded to include the spatial distribution and temporal attenuation that occurs as aquifer stresses propagate through the aquifer to the river. The SRBM is a network flow model in which aquifer characteristics have been introduced through a matrix of response functions. The response functions were determined by independently simulating the effect of a unit stress in each cell of a finite difference groundwater flow model on six reaches of the Snake River. Cells were aggregated into 20 aquifer zones and average response functions for each river reach were included in the SRBM. This approach links many of the capabilities of surface and ground water flow models. Evaluation of an artificial recharge scenario approximately reproduced estimates made by direct simulation in a ground water flow model. The example demonstrated that the method can produce reasonable results but interpretation of the results can be biased if the simulation period is not of adequate duration.     

DYNAMIC RESPONSE OF AQUIFER SYSTEMS TO LOCALIZED RECHARGE1

ABSTRACT. The response of stream-unconfined aquifer systems to localized recharge is investigated by means of a two-dimensional finite element model. A variational approach is used in conjunction with the finite element method to solve the ground water flow equation. Linear approximated triangular elements are used to calculate the hydraulic head distribution in the flow region. The Crank-Nicholson centered scheme of numerical integration is employed to approximate the time derivative in the flow equation. A computer program is developed to calculate the hydraulic head distribution in the flow region. Solutions provided by the finite element model should prove useful in the evaluation of quantitative and qualitative changes in aquifer systems due to natural or artificial recharge. In addition, they should prove useful in the study of irrigation and drainage problems.     

AN ENGINEERING ECONOMIC ANALYSIS OF A PROGRAM FOR ARTIFICIAL GROUNDWATER RECHARGE1

This study describes and demonstrates two alternate methods for evaluating the relative costs and benefits of artificial groundwater recharge using percolation ponds. The first analysis considers the benefits to be the reduction of pumping lifts and land subsidence; the second considers benefits as the alternative costs of a comparable surface delivery system. Example computations are carried out for an existing artificial recharge program in Santa Clara Valley in California. A computer groundwater model is used to estimate both the average long term and the drought period effects of artificial recharge in the study area. For the example problem, the benefits of reduced average annual pumping lifts and reduced incremental subsidence are greater than the total costs of continuing the existing artificial recharge program. Benefits for reduced subsidence are strongly dependent on initial aquifer conditions. The second analysis compares the costs of continuing the artificial recharge program with the costs of a surface system which would achieve the same hydraulic effects. Results indicate that the costs of artificial recharge are considerably smaller than the alternative costs of an equivalent surface system. In evaluating a particular program, consideration should also be given to uncertainties in future supplies and demands for water as well as to the probability of extreme events such as droughts.     

SURFACE WATER-ESKER RECHARGE STUDY EAST LANSING-MERIDIAN TOWNSHIP,MICHIGAN1

ABSTRACT: The East Lansing-Meridian Water and Sewer Authority studied a sand-gravel esker near the existing water treatment plant to determine its potential as an independent surface water supply. The nearby Red Cedar River was also investigated as a possible source of water for immediate treatment or for recharge of the esker. Although the bedrock aquifer (Grand River and Saginaw Formations) yields water adequate for the next 20 years, potential savings in treatment (hardness, iron) and pumping costs, estimated at $30,000 per year for present demand of 5 MGD, are attractive incentives for a surface water-esker recharge program. Operation savings would also be realized by constructing additional bedrock wells in new areas. The river-esker-recharge and new wellfield alternatives are compared for cost-effectiveness. Land costs make the recharge alternative more expensive. The land is undeveloped suburban property with potential for recreational use in conjunction with water supply. More places of outdoor retreat and aesthetics are needed in the Lansig Metropolitan area. A portion of the land costs would have to be borne by these or other interests for the river recharge scheme to be economically feasible.     

Agronomic Water Mass Balance vs. Well Measurement for Assessing Ogallala Aquifer Depletion in the Texas Panhandle

The Ogallala Aquifer is depleting faster than it is being replenished. Interpretation of well data suggests that the water table in some counties is not declining, or not as much as might be expected in view of the amount of land being irrigated. As the Ogallala Aquifer in the Texas Panhandle receives almost no recharge, a possible explanation is that the current method of using well data for estimating the quantity of water remaining in the aquifer is underestimating water in storage. This study used an agronomic water mass balance approach to estimate how much water has been used for irrigation compared to amounts estimated by well data. The major finding was in counties where irrigation well capacities have declined significantly but irrigation is continuing, there is likely more water in storage than presently estimated, but the amounts of water being used for irrigation in those counties are greater than estimated changes of water in storage. The proposed hypothesis for this difference is there are mounds of water between wells that are not being accounted for and data are presented and discussed to support this conjecture.     

AN ECONOMIC ASSESSMENT OF GROUND WATER RECHARGE IN THE TUCSON BASIN1

ABSTRACT: Bringing water from Colorado River via the Central Arizona Project was perceived as the sole solution for Tucson Basin's water problem. Soon after Central Arizona Project's water arrived in Tucson in 1992, its quality provoked a quarrel over its use for potable purposes. A significant outcome of that quarrel was the enactment of the 1995 Proposition 200. The Proposition 200 precludes the use of Central Arizona Project's water for potable purposes, unless it is treated. Yet, it encourages using it for non‐potable purposes and for replenishing the Tucson aquifer through recharge. This paper examines the economic issues involved in utilizing Central Arizona Project's water for recharge. Four planning scenarios were designed to measure and compare the costs and benefits with and without Central Arizona Project's water recharge. Cost‐benefit analysis was utilized to measure recharge costs and benefits and to derive a rough estimate of cost savings from preventing land subsidence. The results indicate that the institutional requirements can be met with Central Arizona Project's water recharge. The economic benefits from reducing pumping cost and saving groundwater are not economically significant. Yet, when combining the use of Central Arizona Project's water for recharge and non‐potable purposes, it demonstrates positive net economic benefits.     

RECHARGE TO ALLUVIAL VALLEY AQUIFERS FROM OVERBANK FLOW AND EXCESS INFILTRATION1

ABSTRACT: Recharge is an important parameter for models that simulate water and contaminant transport in unconfined aquifers. Unfortunately, measurements of actual recharge are not usually available causing recharge to be estimated or possibly added to the calibration procedure. In this study, differences between observed water-table elevations and water-table elevations simulated with a model based on the one-dimensional Boussinesq equation were used to identify both the timing and quantity of recharge to an alluvial valley aquifer. Observed water table elevations and river stage data were recorded during a five-year period from 1991 to 1995 at the Ohio Management Systems Evaluation Area located in south-central Ohio. Direct recharge attributed to overbank flow during and shortly after flood conditions accounted for 65 percent of the total recharge computed during the five-year study period. Recharge of excess infiltration to the aquifer was intermittent and occurred soon after large rainfall events and high river stage. Specification of constant recharge with time values in ground-water simulation models seems inappropriate for stream-aquifer systems given the strong influence of the river on water table elevations in these systems.     

EDWARDS AQUIFER EVALUATION: KINNEY COUNTY,TEXAS1

ABSTRACT: The Edwards Aquifer is one of the most studied and most prolific aquifers in the United States. The aquifer is a heavily fractured and faulted carbonate aquifer with transmissivities in excess of 100 ft²/s. The City of San Antonio relies upon the Edwards Aquifer as its sole source for water. Much work has been done on quantifying recharge to the aquifer and discharge from wells and acquiring aquifer characteristics from pumping tests, specific capacity tests, and geophysical logs. Although the aquifer has been well studied in Bexar County, much less is known about the Edwards Aquifer in Kinney County. This is partly due to the lower population within the county (approximately 3,500 people) relative to the eastern counties (Uvalde, Medina, Bexar, Comal, and Hays) and the great distance of Kinney County from high profile discharge areas such as the City of San Antonio and Comal and San Marcos Springs. Three key products resulted from this study: (1) exploratory well drilling and the largest aquifer test in the county that were conducted to evaluate the well yields within a 10,000 acre study area in which a drawdown of 2.5 ft approximately 1.2 miles away was observed while pumping at approximately 4,600 gpm; (2) a recharge estimate for the Edwards Aquifer within Kinney County of approximately 71,382 ac‐ft/yr; and (3) locating the Brackettville Groundwater Divide from an evaluation of ground water flow direction and hydrograph analysis. These results help evaluate the complex hydraulics occurring within Kinney County and aid in development of ground water modeling that will be used in managing the Edwards Aquifer.     

Impact of Urban Growth and High Residential Irrigation on Streamflow and Groundwater Levels in a Peri‐Urban Semiarid Catchment

The impact of urbanization on groundwater is not simple to understand, as it depends on a variety of factors such as climate, hydrogeology, water management practices, and infrastructure. In semiarid landscapes, the urbanization processes can involve high water consumptions and irrigation increases, which in turn may contribute to groundwater recharge. We assessed the hydrological impacts of urbanization and irrigation rates in an Andean peri‐urban catchment located in Chile, in a semiarid climate. For this purpose, we built and validated a coupled surface–groundwater model that allows the verification of a strong stream–aquifer interaction in areas with shallow groundwater, higher than some sewers and portions of the stream. Moreover, we also identified a significant local recharge associated with pipe leaks and inefficient urban irrigation. From the evaluation of different future scenarios, we found a sustainable water conservation scenario will decrease the current groundwater levels, while the median flow reduces from 408 to 389 L/s, and the low flow (Q_95%) from 43 to 22L/s. Overall, our results show the relevance of integrating the modeling of surface and subsurface water resources at different spatial and temporal scales, when assessing the effect of urban development and the suitability of urban water practices.     

EFFECTS OF ARTIFICIAL RECHARGE ON GROUND WATER QUALITY AND AQUIFER STORAGE RECOVERY1

ABSTRACT: Ground water nitrate contamination and water level decline are common concern in Nebraska. Effects of artificial recharge on ground water quality and aquifer storage recovery (ASR) were studied with spreading basins constructed in the highly agricultural region of the Central Platte, Nebraska. A total of 1.10 million m³ of Platte River water recharged the aquifer through 5000 m² of the recharge basins during 1992, 1993, and 1994. This is equivalent to the quantity needed to completely displace the ground water beneath 34 ha of the local primary aquifer with 13 m thickness and 0.25 porosity. Successful NO₃-N remediation was documented beneath and downgradient of the recharge basins, where NO₃-N declined from 20 to 2 mg L^-1. Ground water atrazine concentrations at the site decreased from 2 to 0.2 mg L^-1 due to recharge. Both NO₃-N and atrazine contamination dramatically improved from concentrations exceeding the maximum contaminant levels to those of drinking water quality. The water table at the site rose rapidly in response to recharge during the early stage then leveled off as infiltration rates declined. At the end of the 1992 recharge season, the water table 12 m downgradient from the basins was elevated 1.36 m above the preproject level; however, at the end of the 1993 recharge season, any increase in the water table from artificial recharge was masked by extremely slow infiltration rates and heavy recharge from precipitation from the wettest growing season in over 100 years. The water table rose 1.37 m during the 1994 recharge season. Resultant ground water quality and ASR improvement from the artificial recharge were measured at 1000 m downgradient and 600 m upgradient from the recharge basins. Constant infiltration rates were not sustained in any of the three years, and rates always decreased with time presumably because of clogging. Scraping the basin floor increased infiltration rates. Using a pulsed recharge to create dry and wet cycles and maintaining low standing water heads in the basins appeared to reduce microbial growth, and therefore enhanced infiltration.     

ESTIMATION OF RECHARGE FROM A RESERVOIR USING TWO WATER BUDGET MODELS1

ABSTRACT: Reservoir water levels, observation well data, and meteorological parameters were collected at a recharge dam site in Central Saudi Arabia. This data, along with other information on the reservoir and the underlying aquifer, were used to estimate the amounts of recharge through the reservoir bed by applying two water budget models. The first is a water budget model for the reservoir only, while the second is for an aquifer reach extending upstream and downstream from the reservoir. The results of the two approaches were discussed and compared.     

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.     

EVALUATING INTERDEPENDENT WATERSHED CONSERVATION AND GROUND WATER MANAGEMENT REFORMS1

Abstract: Conserving the watershed can help to preserve ground water recharge. Preventing overuse of available water through pricing reforms can also substantially increase the value of an aquifer. Inasmuch as users are accustomed to low prices, efficiency pricing may be politically infeasible, and watershed conservation may be considered as an alternative. We estimate and compare welfare gains from pricing reform and watershed conservation for a water management district in Oahu that obtains its water supply from the Pearl Harbor aquifer. We find that pricing reform is welfare superior to watershed conservation unless the latter is able to prevent very large recharge losses. Watershed conservation that yields net gains in combination with pricing reform may cause net losses without the pricing reform. If adoption of watershed conservation delays the implementation of pricing reform, the benefits of the latter are significantly reduced.     

Surface Water Seepage Effects on Shallow Ground‐Water Quality Along the Rio Grande in Northern New Mexico1

Abstract: Interactions between surface irrigation water, shallow ground water, and river water may have effects on water quality that are important for both drinking water supplies and the ecological function of rivers and floodplains. We investigated water quality in surface water and ground water, and how water quality is influenced by surface water inputs from an unlined irrigation system in the Alcalde Valley of the Rio Grande in northern New Mexico. From August 2005 to July 2006, we sampled ground water and surface water monthly and analyzed for concentrations of major cations and anions, specific conductance, pH, dissolved oxygen, and water levels. Results indicate that irrigation ditch seepage caused an increase in ground water levels and that the Rio Grande is a gaining stream in this region. Temporal and spatial differences were found in ion concentrations in shallow ground water as it flowed from under the ditch toward the river. Ground‐water ion concentrations were higher when the ditch was not flowing compared with periods during peak irrigation season when the ditch was flowing. Ditch inputs diluted ion concentrations in shallow ground water at well positions near the ditch. Specifically, lower ion concentrations were detected in ground water at well positions located near the ditch and river compared with well positions located in the middle of an agricultural field. Results from this project showed that ditch inputs influenced ion concentrations and were associated with ground‐water recharge. In arid region river valleys, careful consideration should be given to management scenarios that change seepage from irrigation systems, because in some situations reduced seepage could negatively affect ground‐water recharge and water quality.     

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.     

Rainfall and Spring Discharge Patterns in Two Small Drainage Catchments in the Western Himalayan Mountains, India

Relationship between rainfall and spring discharge study is important to understand hydrological behaviour of springs and water resources management. In the Himalayan mountains springs are the freshwater sources for household consumption. We studied six springs of different recharge area characteristics in two micro-watersheds in western Himalayan mountains in India. Based on the recharge area geology these springs were divided into fracture/joint (FR/JT) and fracture/joint/colluvium (FR/JT/COLL). We found a strong positive relationship between rainfall and spring discharge. Peak spring discharge coincided with peak rainfall in two FR/JT/COLL springs, which was delayed by about one month in FR/JT springs. Mean annual discharge was about two times greater for FR/JT/COLL springs than the FR/JT springs (6.47 vs. 3.94 liter per minute). But spring discharge per 1000 L of rainfall in spring recharge area for FR/JT springs was about 2.3 times greater than the FR/JT/COLL springs (49 vs. 21 liter per minute). In the FR/JT springs, rainfall in spring recharge area and spring discharge were weakly related (r=0.174), while they were strongly related in FR/JT/COLL springs (r=0.595). In the former category of springs decline in discharge was gradual, while it was rapid in the latter category of springs. Therefore, with regard to sustained supply of water for household consumption FR/JT springs can be considered more suitable. Land use and land cover such as moderately grazed pasture, abandoned agricultural terraces and few trees but dense growth of bushes and oak forest in the spring recharge area were found conducive for spring discharge and may be promoted for long-term water resource conservation in this region.