摘要:

An analytical decision model is presented for determining optimal energy extraction rates from hot water geothermal reservoirs when cooled brine is reinjected into the hot water aquifer. This applied economic management model computes the optimal fluid pumping rate and reinjection temperature and the project (reservoir) life consistent with maximum present worth of the net revenues from sales of energy for space heating. The real value of product energy is assumed to increase with time, as is the cost of energy used in pumping the aquifer. The economic model is implemented by using a hydrothermal model that relates hydraulic pumping rate to the quality (temperature) of remaining heat energy in the aquifer. The results of a numerical application to space heating show that profit‐maximizing extraction rate increases with interest (discount) rate and decreases as the rate of rise of real energy value increases. The economic life of the reservoir generally varies inversely with extraction rate. Results were shown to be sensitive to permeability, initial equilibrium temperature, well cost, and well lif

ISSN:0043-1397    

DOI:10.1029/WR017i001p00001

年代:1981

数据来源: WILEY

摘要:

Solid‐set pressurized irrigation system design and operation are studied with optimization techniques to determine the minimum cost distribution system. The principle of the analysis is to divide the irrigation system into subunits in such a manner that the trade‐offs among energy, piping, and equipment costs are selected at the minimum cost point. The optimization procedure involves a nonlinear, mixed integer approach capable of achieving a variety of optimal solutions leading to significant conclusions with regard to the design and operation of the system. Factors investigated include field geometry, the effect of the pressure head, consumptive use rates, a smaller flow rate in the pipe system, and outlet (sprinkler or emitter) discha

ISSN:0043-1397    

DOI:10.1029/WR017i001p00011

年代:1981

数据来源: WILEY

摘要:

A generalized chance‐constrained linear decision rule (LDR) reservoir model is presented which incorporates explicit consideration of the correlation structure of the inflow process. A decision rule which includes predicted flow as a state variable (termed the predictive rule) is contrasted with the rule assuming uncorrelated monthly flows (the independent rule) and a rule which takes knowledge of the upcoming period inflow as given (the Utopian or perfect hindsight rule). Changed feasibility conditions defining minimum and maximum reliable release goals are developed and analyzed. Earlier judgements that LDR models are conservative are examined and contrasted with the improved ability to make reliable release commitments with the predictive rule. Comparison with a target hitting model over a wide range of performance reliabilities shows the new rule to provide consistently more total scheduled releas

ISSN:0043-1397    

DOI:10.1029/WR017i001p00018

年代:1981

数据来源: WILEY

摘要:

A water reuse planning model has been developed for use in determining the optimum reuse of waste‐water on a regional basis that minimizes the overall cost of water supply for single period planning. Wastewater from all use sectors, along with fresh water, are considered as candidate sources or origins of water for other elements within the use sector and also for elements of other use sectors. Quality parameters of various sources of flows are explicitly considered. The model allows for economies of scale in treatment and transportation through the use of a nonlinear objective function and consists of both linear and nonlinear constraints. The model is solved using a large‐scale generalized reduced gradient technique. The analysis of hypothetical examples shows how the model can evaluate various planning scenarios, allowing the planner a broad spectrum of solutions to choose f

ISSN:0043-1397    

DOI:10.1029/WR017i001p00025

年代:1981

数据来源: WILEY

摘要:

A general law for unsteady sediment transport in the form of a differential equation has been established. This law has been tested against the sediment transport rates obtained in the laboratory during aggradation arising from an increase in sediment supply over and above the equilibrium sediment transport capacity of the channel. Using the law, expressions for predicting the maximum depth of aggradation and length of aggradation under the above stated boundary conditions have been obtained. The agreement between values of the parameters computed from these expressions, when compared with the values observed in the laboratory and with the values obtained from the numerical model of Gessler, is very good.

ISSN:0043-1397    

DOI:10.1029/WR017i001p00033

年代:1981

数据来源: WILEY

摘要:

A new method allowing the measurement of rapid water content variations in sandy porous media is reported. The principle of the method is based on the variation of the factor of light transmission through a heterogeneous solid‐liquid‐air medium with water content. The transmission of light through such a medium is favored by the presence of water. The number of pores filled with water as a function of the water content being unknown, it is impossible to predict theoretically the relationship between light transmission and water content, and a calibration procedure is necessary. With proper calibration the present method compares favorably with the gamma ray absorption met

ISSN:0043-1397    

DOI:10.1029/WR017i001p00041

年代:1981

数据来源: WILEY

摘要:

In aquifers containing iron and manganese rich groundwater, groundwater quality can be improved by injecting an oxidizing agent into the aquifer to promote precipitation of iron and manganese. In this study, oxygen rich water was recharged by an injection well. Concentration measurements were carried out around the well at different locations to find out the demand for oxygen to oxidize iron (II) within the aquifer. Evaluation and interpretation of the field experiments were made by comparison with a mathematical model. The experiments and in particular the model calculations show that the method is practicable and economic.

ISSN:0043-1397    

DOI:10.1029/WR017i001p00049

年代:1981

数据来源: WILEY

摘要:

A traveling wave solution was derived for the problem of simultaneous flow of water and air through homogeneous porous media. It is found that the properties of the solution generally depend upon the hydraulic characteristics of a given problem. The properties of the solution are presented for a specific case in which the hydraulic characteristics are given in specific functional forms. For this specific case it is found that a singularity occurs in the solution at both a saturated‐unsaturated boundary and a wetting front. Some applications of the solution are discusse

ISSN:0043-1397    

DOI:10.1029/WR017i001p00057

年代:1981

数据来源: WILEY

摘要:

Steady interflow of water in the near‐surface saturated soil horizons, which are the important nonpoint sources of applied agricultural chemicals appearing in field runoff, is investigated theoretically. Analytical solutions are obtained for some relevant cases of interflow in a sloping layered soil having a subsoil of lower permeability. Analysis is made for the effect of the relative permeability of the subsoil and of the depth of the subsoil above an impermeable base varying from zero to infinity, in relation to different ratios of slope length to soil profile depth. Solutions and analyses are also extended to a case where flow through the topsoil is saturated and steady, but where the subsoil is still accepting a constant downward flux of water uniformly over all its area. The solutions are for a rectangularly bounded, tilted flow medium; but for long slopes the details of the flow medium boundaries at the top and bottom ends should have negligible effects on overall flow. The results show that the interflow through each horizon of a layered soil profile can be approximated by a one‐dimensional Darcian flow parallel to the slope, if the ratio of slope length to soil profile depth is greater than about 6 to 10. This extends the finding reported earlier in the literature for a uniform soil. For an extreme case of a sloping soil with a semi‐infinitely deep subsoil on an impermeable base, the interflow through the topsoil, if it is highly conductive compared to the subsoil, can still be treated as a one‐dimensional flow. For such cases, the movement of soil chemicals with interflow can be described as a one‐dimensional miscible displacement process. A uniformly constant downward flux of water into the subsoil decreases interflow through the topsoil. The extent of the decrease depends upon the land slope and the relative conductivity of the subsoil. Of even greater significance for chemical transport is the finding that the cross section of the topsoil through which the interflow traverses and picks up its chemical load is drastically reduced by downward leakage, even when the subsoil conductivity is two orders of magnitude smaller than that of the topsoil. A simplified prediction of this region of interflow is deduced from the results. By representing this wedge‐shaped area by an equivalent rectangle, the chemical movement, for a first‐order estimation in field application, may still be approximated as a one‐dimension

ISSN:0043-1397    

DOI:10.1029/WR017i001p00065

年代:1981

数据来源: WILEY

摘要:

Laboratory experiments have shown that compacted clays act as osmotic membranes when they separate aqueous solutions of unequal ionic concentration. Theoretically, osmotically induced differential hydraulic pressure in groundwater systems can be relatively high. The magnitude depends primarily upon concentration differences across the membrane, type of ions, type of clay, and pore size. In experiments, thin, compacted clay membranes commonly exhibit varying degrees of osmotic efficiency due to ion leak‐age through the clay. In natural systems the membrane and the solution containers are not as distinct and well defined as they are in the laboratory. Moreover, the membrane is commonly thick, inhomogeneous, and composite. In a buried Triassic basin at the Savannah River plant near Aiken, South Carolina, it is suspected that osmosis causes the saline water in the basin center to be slightly geopressurized in relation to freshwater in the overlying coastal plain aquifer. Two wells have heads of 7.88 and 12.98 bars (114.3 and 188.3 psi) above the head in the coastal plain aquifer. The head in each of these wells approximates the osmotic equilibrium head calculated from solution concentration of water produced by each well (12,000 and 18,500 mg/l, respectively). Other wells penetrating the top and edge of the Triassic basin probably penetrate a zone where ion leakage gives rise to less saline water. Thus these wells are not geopressurize

ISSN:0043-1397    

DOI:10.1029/WR017i001p00073

年代:1981

数据来源: WILEY