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.     

Evaluating the impact of water conservation on fate of outdoor water use: a study in an arid region

In this research, the impact of several water conservation policies and return flow credits on the fate of water used outdoors in an arid region is evaluated using system dynamics modeling approach. Return flow credits is a strategy where flow credits are obtained for treated wastewater returned to a water body, allowing for the withdrawal of additional water equal to the amount returned as treated wastewater. In the return credit strategy, treated wastewater becomes a resource. This strategy creates a conundrum in which conservation may lead to an apparent decrease in water supply because less wastewater is generated and returned to water body. The water system of the arid Las Vegas Valley in Nevada, USA is used as basis for the dynamic model. The model explores various conservation scenarios to attain the daily per capita demand target of 752 l by 2035: (i) status quo situation where conservation is not implemented, (ii) conserving water only on the outdoor side, (iii) conserving water 67% outdoor and 33% indoor, (iv) conserving equal water both in the indoor and outdoor use (v) conserving water only on the indoor side. The model is validated on data from 1993 to 2008 and future simulations are carried out up to 2035. The results show that a substantial portion of the water used outdoor either evapo-transpires (ET) or infiltrates to shallow groundwater (SGW). Sensitivity analysis indicated that seepage to groundwater is more susceptible to ET compared to any other variable. The all outdoor conservation scenario resulted in the highest return flow credits and the least ET and SGW. A major contribution of this paper is in addressing the water management issues that arise when wastewater is considered as a resource and developing appropriate conservation policies in this backdrop. The results obtained can be a guide in developing outdoor water conservation policies in arid regions.     

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.     

Hydrologic Model Framework for Water Resources Planning in the Santa Cruz River,Southern Arizona1

Abstract: The authors develop a model framework that includes a set of hydrologic modules as a water resources management and planning tool for the upper Santa Cruz River near the Mexican border, Southern Arizona. The modules consist of: (1) stochastic generation of hourly precipitation scenarios that maintain the characteristics and variability of a 45‐year hourly precipitation record from a nearby rain gauge; (2) conceptual transformation of generated precipitation into daily streamflow using varied infiltration rates and estimates of the basin antecedent moisture conditions; and (3) surface‐water to ground‐water interaction for four downstream microbasins that accounts for alluvial ground‐water recharge, and ET and pumping losses. To maintain the large inter‐annual variability of streamflow as prevails in Southern Arizona, the model framework is constructed to produce three types of seasonal winter and summer categories of streamflow (i.e., wet, medium, or dry). Long‐term (i.e., 100 years) realizations (ensembles) are generated by the above described model framework that reflects two different regimes of inter annual variability. The first regime is that of the historic streamflow gauge record. The second regime is that of the tree ring reconstructed precipitation, which was derived for the study location. Generated flow ensembles for these two regimes are used to evaluate the risk that the regional four ground‐water microbasins decline below a preset storage threshold under different operational water utilization scenarios.     

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.     

MATHEMATICAL ANALYSIS OF ARTIFICIAL RECHARGE FROM BASINS1

ABSTRACT: One of the most common methods of artificial recharge to the ground water is from basins. In this paper, seven analytical solutions that describe artificial recharge from basins are presented. Most of these solutions are derived by directly solving the general partial differential equation for ground water flow. The solutions differ in that they use different boundary conditions, basin shapes, and consider the nonlinearity of the artificial recharge problem differently. Use of each analytical solution is demonstrated in this paper by application to an example problem. A comparison of each analytical solution presented in this paper was made to give suggestions on their use, their ease of implementation, and their relative agreement. Although no attempt is made in the paper to conclude which analytical solution is best for all problems, some general conclusions can be stated on the applicability of the various analytical solutions. Of the analytical solutions presented in this paper, Glovers and Hantush's solutions for rectangular recharge basins are highly recommended. Baumanns solution for a circular basin also gave fairly reliable results and is very easy to evaluate numerically.     

GROUND WATER MONITORING NETWORK DESIGN USING MULTIPLE CRITERIA DECISION MAKING ANT) GEOSTATISTICS1

ABSTRACT: A multi-criteria approach to ground water quality monitoring network design is developed. The methodology combines multi-criteria decision making (MCDM) and modifications of geostatistical variance reduction analysis. Composite programming, a distance based optimization algorithm that employs a hierarchial structure, is used for the MCDM component of the design methodology. MCDM allows the consideration of numerous, often conflicting, design criteria. The methodology is useful for identifying the preferred combination of direct borehole and indirect geo-electric data. It also permits the use of prior information during initial stages of network development. Multi-variate kriging is employed to evaluate network performance using the combination of direct borehole data and indirect geoelectric data. Weighted measures of estimation variance are used as primary measures of performance, with the reduction in estimation variance being computed by the fictitious point method. Case study results demonstrate that the network design methodology can be used in both early and late phases of network development. It also leads to selection of the preferred combination and spatial orientation of direct and indirect data sources while considering cost-effectiveness and performance of alternative designs.     

Use of Streamflow Data to Estimate Base Flow/Ground‐Water Recharge For Wisconsin1

Abstract: The average annual base flow/recharge was determined for streamflow‐gaging stations throughout Wisconsin by base‐flow separation. A map of the State was prepared that shows the average annual base flow for the period 1970‐99 for watersheds at 118 gaging stations. Trend analysis was performed on 22 of the 118 streamflow‐gaging stations that had long‐term records, unregulated flow, and provided aerial coverage of the State. The analysis found that a statistically significant increasing trend was occurring for watersheds where the primary land use was agriculture. Most gaging stations where the land cover was forest had no significant trend. A method to estimate the average annual base flow at ungaged sites was developed by multiple‐regression analysis using basin characteristics. The equation with the lowest standard error of estimate, 9.5%, has drainage area, soil infiltration and base flow factor as independent variables. To determine the average annual base flow for smaller watersheds, estimates were made at low‐flow partial‐record stations in 3 of the 12 major river basins in Wisconsin. Regression equations were developed for each of the three major river basins using basin characteristics. Drainage area, soil infiltration, basin storage and base‐flow factor were the independent variables in the regression equations with the lowest standard error of estimate. The standard error of estimate ranged from 17% to 52% for the three river basins.     

CONTROL OF NATURAL BRINE SPRINGS IN BRAZOS RIVER BASIN PART II: BRINE DISPOSAL1

ABSTRACT: Water quality in the Brazos River of Texas is seriously degraded by natural salt pollution. Two thousand tons/day of total dissolved solids emanate from brine springs and seeps in the Upper Brazos River drainage. Approximately 45 percent of the total salt load comes from a relatively small flow in the Dove Creek area. The companion paper demonstrates that a system of wells pumping brine at a constant rate of about 2 cfs from the near surface aquifer should eliminate the brine springs in this area. In this paper, injection into deep brine aquifers is shown to be a feasible brine disposal alternative. Four brine aquifers were determined from the literature to be possible injection zones. Accurate net aquifer thickness maps were generated in a 23 by 14 mile area centered on the Dove Creek area for three of the aquifers from an interpretation of 41 well logs. Constant injection for a project life of 100 years was simulated using the SWIFT/486 software. Modeling suggests that one well would be sufficient to inject the entire disposal volume into either the Strawn or Ellenburger Formation.     

HYDROLOGIC RESPONSE TO PUMPING AND CONTAMINANT ADVECTION IN A FRACTURED ROCK ENVIRONMENT1

ABSTRACT: Ground water flow and supply at the Whiteshell Research Area (WRA) in southeastern Manitoba and the advective movement of contaminants from a hypothetical nuclear fuel waste disposal vault to the adjacent biosphere and a nearby ground water supply well are simulated using finite-element modeling and numerical particle-tracking technique. The hypothetical vault is located at a depth of 500 m, below the water table, in low-permeability plutonic rock of the Canadian Shield. The rock mass is intersected by high-permeability fracture zones (aquifers), which also act as conduits for vault contaminants to migrate to the ground surface. The ground water resource is, therefore, limited in quantity and quality and should be explored with care. A 30 m deep well, which pumps water at a rate of 120 m³/yr from a low-dipping fracture zone, LD1, reduces natural discharge from the system to augment natural recharge. At this pumping rate, a 100 m or 200 m deep well neither reduces discharge nor induces recharge into the system. Thus, at the WRA, a 30 m deep domestic water supply well best meets the water requirements of a one-person household at the rate of 120 m³/yr. The 100 m and 200 m wells best meet the requirements of a family of six and a family of six with light irrigation, respectively, without capturing contaminants’pathways from the vault to the ground surface. By virtue of the proximity of the 200 m well intake to the hypothetical vault, this well performs best as a purge well at pumping rates of 0,000 m³/yr and greater. Finite-element modeling is useful in evaluating the water supply potential of a fractured rock environment in which a nuclear waste disposal vault is proposed to be sited.     

A system dynamics model to facilitate public understanding of water management options in Las Vegas,Nevada

Water managers increasingly are faced with the challenge of building public or stakeholder support for resource management strategies. Building support requires raising stakeholder awareness of resource problems and understanding about the consequences of different policy options. One approach that can help managers communicate with stakeholders is system dynamics modeling. Used interactively in a public forum, a system dynamics model can be used to explain the resource system and illustrate the effects of strategies proposed by managers or suggested by forum participants. This article illustrates the process of building a strategic-level system dynamics model using the case of water management in Las Vegas, Nevada. The purpose of the model was to increase public understanding of the value of water conservation in Las Vegas. The effects of policies on water supply and demand in the system are not straightforward because of the structure of the system. Multiple feedback relationships lead to the somewhat counterintuitive result that reducing residential outdoor water use has a much greater effect on water demand than reducing indoor water use by the same amount. The model output shows this effect clearly. This paper describes the use of the model in research workshops and discusses the potential of this kind of interactive model to stimulate stakeholder interest in the structure of the system, engage participant interest more deeply, and build stakeholder understanding of the basis for management decisions.     

SIMULATING THREE-DIMENSIONAL GROUND WATER RESPONSE IN A SMALL MOUNTAINOUS WATERSHED1

ABSTRACT: Snowmelt from deep mountainous snowpacks is seldom rapid enough to exceed infiltration rates; thus, the source of streamflow in many mountainous watersheds is snowmelt recharge through shallow ground water systems. The hydrologic response and interaction between surface and sub-surface flow processes in these watersheds, which is controlled by basin structure, the spatial distribution of snowmelt, and the hydrogeology of the subsurface, are not well understood. The purpose of this study was to test a three-dimensional ground water model using simulated snowmelt input to simulate ground water response to spatially distributed snowmelt on the Upper Sheep Creek Watershed located within the Reynolds Creek Experimental Watershed in Southwestern Idaho. The model was used to characterize the mountainous aquifer and to delineate the subsurface flow mechanisms. Difficulty in finding a reasonable combination of grid spacing and time stepping within the model was encountered due to convergence problems with the Picard solution to the non-linear variably saturated ground water flow equations. Simulation results indicated that flow may be either unconfined or confined depending on inflow rate and hydrogeologic conditions in the watershed. The flow mechanism had a much faster response time when confined flow occurred. Response to snowmelt from a snow drift approximately 90 m away took only a few hours when flow was confined. Simulated results showed good agreement with piezometer measurements both in magnitude and timing; however, convergence problems with the Picard solution limited applicability of the model.     

ARTIFICIAL RECHARGE IN SASKATCHEWAN: CURRENT DEVELOPMENTS1

ABSTRACT: The use of artificial recharge in Saskatchewan and the rest of Canada to improve rural community and farmstead domestic water supply has great potential. Approximately 75 percent of the people in rural Saskatchewan and 26 percent of all the people in Canada are dependent on ground water for their domestic water supply. Typically, this water is highly mineralized and is often unpalatable due to odor and taste. A source of readily available, high quality water to eliminate expensive chemical treatment of available water and long distance hauling would be of significant value to rural residents. Storage of high quality water in aquifers by injection through wells has been documented and has been shown to depend on the use of a surface water catchment system to provide the high quality water. Since air entrainment or formation clogging can occur in poorly operated recharge schemes, development of proper design and operation of recharging procedure is required. This can be accomplished by using an injection response computer model and a properly designed injection system. Small scale artificial recharge projects will provide a valuable commodity to rural water users and will promote sustainable and conjunctive use of surface and ground water resources.     

A CRAZY IDEA ON URBAN WATER MANAGEMENT?1

ABSTRACT. High percentage of imperviousness in the city is the source of storm runoff. Roof area contributes significantly to the imperviousness. An attempt to make use of roofs as urban flood control device and water conservation measure is advocated. Two different schemes, one for built-up industrial-commercial area, the other for residential area, are suggested. The former utilizes the roof as detention reservoir for flood control, the latter employs recharge pit to convert runoff into ground water resource. The proposed schemes are not only hydrologically, hydraulically and structurally sound but also economically feasible. It is worth considering in the future planning of urban renewal and urban development.