A stochastic optimization framework for the restoration of an over-exploited aquifer

Abstract

This study investigates the impact of hydraulic conductivity uncertainty on the sustainable management of the aquifer of Lake Karla, Greece, using the stochastic optimization approach. The lack of surface water resources in combination with the sharp increase in irrigation needs in the basin over the last 30 years have led to an unprecedented degradation of the aquifer. In addition, the lack of data regarding hydraulic conductivity in a heterogeneous aquifer leads to hydrogeologic uncertainty. This uncertainty has to be taken into consideration when developing the optimization procedure in order to achieve the aquifer's sustainable management. Multiple Monte Carlo realizations of this spatially-distributed parameter are generated and groundwater flow is simulated for each one of them. The main goal of the sustainable management of the 'depleted' aquifer of Lake Karla is twofold: to determine the optimum volume of renewable groundwater that can be extracted, while, at the same time, restoring its water table to a historic high level. A stochastic optimization problem is therefore formulated, based on the application of the optimization method for each of the aquifer's multiple stochastic realizations in a future period. In order to carry out this stochastic optimization procedure, a modelling system consisting of a series of interlinked models was developed. The results show that the proposed stochastic optimization framework can be a very useful tool for estimating the impact of hydraulic conductivity uncertainty on the management strategies of a depleted aquifer restoration. They also prove that the optimization process is affected more by hydraulic conductivity uncertainty than the simulation process.

Nutrient Concentrations in Seven Irrigation Reservoirs (Lake Karla Watershed Thessaly Greece)

“…According to the database of CORINE Land Cover 2000 for Greece [14], almost 68% of the basin surface is being cultivated, being one of the most productive agricultural regions of Greece. The major crops are cotton, wheat, alfa-alfa, corn, tobacco and orchards [15]. The main basin's water resources consumption occurs to cover the irrigation needs of these cultivations.…”

Preface—Special Issue: Facets of Uncertainty

“…Tyralla and Schumann (2016) present a new approach for dealing with model structural uncertainty. Mylopoulos and Sidiropoulos (2016) consider the management of an aquifer under uncertain hydrogeology of the subsurface and propose a stochastic optimization approach, while Mukolwe et al (2016) deal with uncertainties on the surface, studying the influence of various elevation datasets on accuracy of flooding models. Kabeya et al (2016) quantify the effects of forest harvesting versus climate on streamflow variability and trend, while Koga et al (2016) present an urban-scale hydrological application accounting for the uncertainty in land-use delineation.…”

Quantitative Classification of Desertification Severity for Degraded Aquifer Based on Remotely Sensed Drought Assessment

“…The study area of 500 km 2 is extensively cultivated with water demanding crops such as maize, cotton, and alfalfa. About 98% of the groundwater resources are used to cover the irrigation needs through unregistered private pumping wells [10]. At the north of the area, an old irrigation network exists which is consisted of small reservoirs and open channels.…”

“…No-flow conditions were assigned to the eastern and southeastern boundary of the aquifer, because of the presence of schist. The estimation of extracted groundwater volume from wells and its use have been analytically presented by [10]. The mean annual volume of water demand for irrigation needs is 124 hm 3 , and for domestic use is 3 hm 3 .…”

“…As a result, soluble salts within irrigation waters may exceed critical thresholds. Moreover, leaching requirements may not be met by irrigation scheduling, and intrusion of seawater may occur due to overpumping of coastal aquifers [10][11][12]. Chemical desertification affects fertile agricultural land and it is usually localized in alluvial plains.…”