In this paper, we have investigated minimization of total cost to pump a given flow rate from any number (n) of wells up to a water tank, under steady-state flow conditions. Regarding groundwater flow, we have considered infinite or semi-infinite aquifers, to which the method of images applies. Additional regional groundwater flow can be taken into account, too. The pipe network connecting the wells to the tank can include junctions at the locations of the wells only. Moreover, all pumps have equal efficiency. We have derived a new analytical formula, which holds at the critical points of the total cost function. Based on this formula, we derived a system of n equations and n unknowns, to calculate the well flow rate combinations which correspond to the critical points of the total cost function. The n-1 equations are 2nd degree polynomials, while the remaining one is linear, expressing the constraint that the sum of well flow rates must be equal the required total flow rate. The solution of the system can be achieved using commercial solvers. Moreover, we have concluded that there is one feasible solution that minimizes the total cost. Finally, we present a tabulation process to facilitate the use of solvers and we provide and discuss two illustrative examples.

This paper deals with water pumping cost minimization, in a confined infinite aquifer, proposing an alternate pulsed pumping schedule. The transient flow analysis is conducted for two wells with equal pumping rates. Specifically, two pumping schedules are analytically compared. In the first case, well users pump simultaneously, and in the second one they cooperate so that they pump alternately. This paper proves that the proposed alternate pumping schedule works as a stabilizer, reducing the high hydraulic drawdowns values, regardless of the aquifer characteristics. Moreover, pumping alternately is better in terms of pumping cost, compared to simultaneous pumping, though benefit become negligible as distance between wells becomes large. Two simplified equations are proposed, one to find the difference of the hydraulic drawdowns between the two pumping schedules and the other one to find the economic benefit of each well from cooperation. The equations are finally applied to a number of cases and their results are compared to the results obtained from an algorithm created to calculate the hydraulic drawdowns and the pumping cost, using the Theis equation. The results can be very useful in irrigation scheduling, as they can be applied to systems of well users/farmers, to reduce pumping cost.

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Minimization of groundwater exploitation cost is examined, considering: (a) Pumping from a system of wells up to a central water tank, including friction losses along the connecting pipe network and (b) amortization of network construction. Assuming that the wells are located symmetrically around the tank and directly connected to it, we derived analytically the distance between tank and wells, which minimizes the total cost. Then we compared the minimum cost of this well layout, with that of placing one well at the location of the tank and the rest symmetrically around it. Finally, we dropped any assumption on well layout, we considered that wells are connected to the tank using a minimum spanning tree and we optimized well locations and flow rates using genetic algorithms. For up to 8 wells, the resulting minimum cost is comparable to that of the symmetrical cases, even when the optimal well layout is quite different. Moreover, the analytical solution, derived for the symmetrical case, can serve to evaluate solutions achieved by sophisticated optimization techniques.

In this paper, an integrated methodology is developed to determine optimum areas for Photovoltaic (PV) installations that minimize the relevant visual disturbance and satisfy spatial constraints associated with land use, as well as environmental and techno-economic siting factors. The visual disturbance due to PV installations is quantified by introducing and calculating the “Social Disturbance” (SDIS) indicator, whereas optimum locations are determined for predefined values of two siting preferences (maximum allowable PV locations—grid station distance and minimum allowable total coverage area of PV installations). Thematic maps of appropriate selected exclusion criteria are produced, followed by a cumulative weighted viewshed analysis, where the SDIS indicator is calculated. Optimum solutions are then determined by developing and employing a Genetic Algorithms (GAs) optimization process. The methodology is applied for the municipality of La Palma Del Condado in Spain for 100 different combinations of the two siting preferences. The optimization results are also employed to create a flexible and easy-to-use web-GIS application, facilitating policy-makers to choose the set of solutions that better fulfils their preferences. The GAs algorithm offers the ability to determine distinguishable, but compact, regions of optimum locations in the region, whereas the results indicate the strong dependence of the optimum areas upon the two siting preferences.

In this paper, we examine the accuracy of estimating the hydrogeological parameters, transmissivity (T) and storativity (S), in a confined aquifer, when there are not enough available data for pumping flow rate values. While the most popular methods, used to estimate aquifer characteristics, assume that the pumping flow rate is constant during pumping, this is practically infeasible. Violation of this assumption results in errors, which are examined in this paper using field drawdown measurements. To find the aquifer characteristics, we use two methods, testing various pumping flow rates. At first, we employ the Cooper–Jacob equations to calculate (T) and (S) values. Afterwards we use these values to create hypothetical drawdowns using Theis equation and finally we estimate the Root Mean Square Error (RMSE) between the actual and the hypothetical drawdowns. Then, we repeat the same process, replacing the Cooper–Jacob equations with Genetic Algorithms and Theis equation to find the aquifer characteristics by minimizing the RMSE between the actual and the hypothetical drawdowns. Even though the process is applied only in three datasets, the results indicate that regardless of the method used, the obtained values of aquifer characteristics (T, S) are not considerably affected by inaccurate pumping flow rate estimations.

In this article, alternate pumping is studied as a means used to reduce the salinity concentration in coastal aquifers, pumped using a system of wells. This approach has been applied to a hypothetical confined coastal aquifer. Flow has been modeled, using SEAWAT. Two strategies are proposed based on cooperative game theory, to promote alternate pumping. In both strategies an external player will compensate the users that will pump during an unpopular pumping period. In the first strategy it is supposed that this external player aims at protecting a critical well, e.g. a municipal well, reducing its maximum salinity concentration by pumping alternately. In the second strategy proposed, the target is to reduce the overall salinity of the water pumped by the wells. In applying the cooperative game theory, the Shapley value is used to distribute the benefits of cooperation between the players (well users), according to their marginal contribution. Overall, well users can reduce sea water intrusion by cooperatively changing their pumping time schedules. The game theoretical model developed is a useful tool to promote cooperation toward this direction. The methods applied in the hypothetical aquifer, can be tested in actual aquifers to reduce sea water intrusion.

In this paper, groundwater pumping schedules are examined, in terms of pumping energy consumption minimization. Chromatic graphs are used for the first time to assign groundwater pumping schedules. Assuming that a finite number of users pumps from a common aquifer, we examine the following 3 pumping scenarios: (a) all users pump simultaneously (b) users pump during one out of 2 different periods (c) users pump during one out 4 different periods. A computational code, based on Theis equation, is constructed to calculate the drawdowns and, subsequently, the energy consumption, for various well locations, numbers of wells, flow rates, pumping period durations and aquifers' characteristics. We use Nearest Neighbor Graphs and Chromatic Graphs, to represent the interactions of the well users.. We compare the results obtained when Chromatic Graphs are used, to the optimum, which is obtained using Genetic Algorithms. Our results indicate that: (a) performance of chromatic graphs is good (b) when 2 pumping periods are used, it is sufficient for each player to cooperate with their nearest neighbor and pump alternately. In typical cases the energy consumption reduction can be around 10–40%. The benefit is even higher if 4 pumping periods are used.