Jens Grundmann

Towards an integrated arid zone water management using simulation-based optimisation

For ensuring both optimal sustainable water resources management and long-term planning in a changing arid environment, we propose an integrated Assessment-, Prognoses-, Planning- and Management tool (APPM). The new APPM integrates the complex interactions of the strongly nonlinear meteorological, hydrological and agricultural phenomena, considering the socio-economic aspects. It aims at achieving best possible solutions for water allocation, groundwater storage and withdrawals including saline water management together with a substantial increase of the water use efficiency employing novel optimisation strategies for irrigation control and scheduling. To obtain a robust and fast operation of the water management system, it unites process modeling with artificial intelligence tools and evolutionary optimisation techniques for managing both water quality and quantity. We demonstrate some key components of our methodology by an exemplary application to the south Al-Batinah region in the Sultanate of Oman which is affected by saltwater intrusion into a coastal aquifer due to excessive groundwater withdrawal for irrigated agriculture. We show the effectiveness and functionality of a new simulation-based water management system for the optimisation and evaluation of different irrigation practices, crop pattern and resulting abstraction scenarios. The results of several optimisation runs indicate that due to contradicting objectives, such as profit-oriented agriculture versus aquifer sustainability only a multi-objective optimisation can provide sustainable solutions for the management of the water resources in respect of the environment as well as the socio-economic development.

Saltwater intrusion modeling: Verification and application to an agricultural coastal arid region in Oman

This paper deals with numerical modeling of density-dependent flow of saltwater intrusion in coastal groundwater systems. We present the implementation of an approach to solve a moving boundary problem for a dynamic water table within an invariant finite element mesh. The model is successfully validated against laboratory experiment data for an unconfined, density-dependent benchmark. The validated software is applied to a regional-scale study area and sufficiently calibrated for a steady state of pre-development conditions. Transient mass transport scenario simulations show good concordance with salinity measurements satisfyingly supporting the model setup.

Assessing the saltwater remediation potential of a three-dimensional, heterogeneous, coastal aquifer system

This paper evaluates the remediation potential of a salinized coastal aquifer by utilizing a scenario simulation. Therefore, the numerical model OpenGeoSys is first validated against analytical and experimental data to represent transient groundwater level development and variable density saline intrusion. Afterwards, a regional scale model with a three-dimensional, heterogeneous hydrogeology is calibrated for a transient state and used to simulate a best-case scenario. Water balances are evaluated in both the transient calibration and scenario run. Visualization techniques help to assess the complex model output providing valuable insight in the occurring density-driven flow processes. Furthermore, modeling and visualization results give information on the time scale for remediation activities and, due to limitations in data quality and quantity reveal potential for model improvement.

Sustainable management of a coupled groundwater-agriculture hydrosystem using multi-criteria simulation based optimisation.

In this paper we present a new simulation-based integrated water management tool for sustainable water resources management in arid coastal environments. This tool delivers optimised groundwater withdrawal scenarios considering saltwater intrusion as a result of agricultural and municipal water abstraction. It also yields a substantially improved water use efficiency of irrigated agriculture. To allow for a robust and fast operation we unified process modelling with artificial intelligence tools and evolutionary optimisation techniques. The aquifer behaviour is represented using an artificial neural network (ANN) which emulates a numerical density-dependent groundwater flow model. The impact of agriculture is represented by stochastic crop water production functions (SCWPF). Simulation-based optimisation techniques together with the SCWPF and ANN deliver optimal groundwater abstraction and cropping patterns. To address contradicting objectives, e.g. profit-oriented agriculture vs. sustainable abstraction scenarios, we performed multi-objective optimisations using a multi-criteria optimisation algorithm.

Multiobjective parameter estimation of hydraulic properties for a sandy soil in Oman

The estimation of soil hydraulic parameters for the description of the highly non-linear hydraulic conductivity and water retention curve is of crucial importance for numerical modeling of water and solute transport in the vadose zone. Soil cores have been taken from different depths of a sandy soil of an agricultural field site located in the Batinah region of the Sultanate of Oman and subjected to a comprehensive laboratory analysis, comprising simplified multistep outflow experiments without the use of microtensiometers, additional retention measurements with the pressure plate apparatus and particle size analysis. The measured retention curve and the dynamic cumulated outflow time series—characterizing the hydraulic conductivity curve—are used to estimate the soil hydraulic parameters of the Mualem-van Genuchten (MvG) soil model. Multiobjective parameter optimization runs were performed by coupling the HYDRUS-1D model with the AMALGAM algorithm to allow an enhanced diagnostics of the soil and model behavior by analyzing the trade-offs between two objectives. Furthermore, two different formulations of the MvG model were investigated regarding their ability to reproduce the measurements: (1) P1—with fixed shape parameter

An integrated approach to conceptualise hydrological and socio-economic interaction for supporting management decisions of coupled groundwater–agricultural systems

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Integrated Modeling System for Flash Flood Routing in Ephemeral Rivers under the Influence of Groundwater Recharge Dams

τ and (2) P2—considering the shape parameter