Excessive Groundwater Withdrawal Research Articles

The deformation behavior of soil mass in the subsidence region of Beijing, China

Abstract. Land subsidence induced by excessive groundwater withdrawal has been a major environmental and geological problem in the Beijing plain area. The monitoring network of land subsidence in Beijing has been established since 2002 and has covered the entire plain area by the end of 2008. Based on data from extensometers and groundwater observation wells, this paper establishes curves of variations over time for both soil mass deformation and water levels and the relationship between soil mass deformation and water level. In addition, an analysis of deformation behavior is carried out for soil mass with various lithologies at different depths depending on the corresponding water level. Finally, the deformation behavior of soil mass is generalized into five categories. The conclusions include: (i) the current rate of deformation of the shallow soil mass is slowing, and most of the mid-deep and deep soil mass continue to compress at a more rapid speed; (ii) the sand strata behaves elastically, while the clay soil mass at different depths is usually characterized by elastic-plastic and creep deformation, which can be considered as visco-elastoplastic.

Numerical simulation of earth fissures due to groundwater withdrawal

Abstract. Excessive groundwater withdrawal can cause land subsidence and earth fissures. The initiation and propagation of earth fissures are related to tensile failure and crack propagation in soils. Based on fracture mechanics, the crack band model (CBM), one of the smear crack models which is relatively easy to construct and convenient to be integrated into standard finite element codes is used in this paper. The calculated results of CBM are less dependent on the sizes of finite elements. The model was applied to simulate the formation and propagation of earth fissures in the hydrostratigraphic units with a bedrock ridge. The simulated positions and patterns of earth fissures coincide with field observations, suggesting that the modeling approach is adept to simulate the initiation and propagation of earth fissures due to groundwater withdrawal.

Land subsidence and earth fissures in south-central and southern Arizona, USA

Land subsidence due to groundwater overdraft has been an ongoing problem in south-central and southern Arizona (USA) since the 1940s. The first earth fissure attributed to excessive groundwater withdrawal was discovered in the early 1950s near Picacho. In some areas of the state, groundwater-level declines of more than 150 m have resulted in extensive land subsidence and earth fissuring. Land subsidence in excess of 5.7 m has been documented in both western metropolitan Phoenix and Eloy. The Arizona Department of Water Resources (ADWR) has been monitoring land subsidence since 2002 using interferometric synthetic aperture radar (InSAR) and since 1998 using a global navigation satellite system (GNSS). The ADWR InSAR program has identified more than 25 individual land subsidence features that cover an area of more than 7,300 km2. Using InSAR data in conjunction with groundwater-level datasets, ADWR is able to monitor land subsidence areas as well as identify areas that may require additional monitoring. One area of particular concern is the Willcox groundwater basin in southeastern Arizona, which is the focus of this paper. The area is experiencing rapid groundwater declines, as much as 32.1 m during 2005–2014 (the largest land subsidence rate in Arizona State—up to 12 cm/year), and a large number of earth fissures. The declining groundwater levels in Arizona are a challenge for both future groundwater availability and mitigating land subsidence associated with these declines. ADWR’s InSAR program will continue to be a critical tool for monitoring land subsidence due to excessive groundwater withdrawal.

Role of hydrogeochemical process in increasing groundwater salinity in the central Godavari delta

Groundwater salinization is an ever increasing problem in coastal aquifers due to seawater intrusion resulting from excessive groundwater withdrawals, lithological conditions of the aquifer and industrial and agriculture pollutant loads. Identification of salinity sources is challenging and a prerequisite for the protection of coastal fresh water aquifers. The present aim of the study is to identify the salinity sources and to understand its dynamics in the central Godavari delta, Andhra Pradesh where groundwater is highly saline with total dissolved solids (TDS) of ∼5000 mg/L at shallow depths of <3 m bgl. Groundwater samples were collected from 42 representative observation wells in the area and analyzed for major ions and stable isotopes (δ18O). Different hydro-chemical mixing models and multivariate statistical techniques, including factor and cluster analysis, are applied to these data sets. The results revealed that very high salinity (∼25,000 mg/L) in pumping wells is due to up-coning of salt water and the salinity is palaeo in origin. The salinity in the wells along the drains and near the coast (∼10,000 mg/L) is due to the infiltration of marine waters resulting from backwaters and intrusion of seawater along the drains. The salinity (∼5000 mg/L) in the wells away from the coast is attributed to dissolution of evaporites in the groundwater and ion exchange process.

Mechanisms for earth fissure formation due to groundwater extraction in the Su-Xi-Chang area, China

Excessive groundwater withdrawal has caused many earth fissures in the cities of Suzhou, Wuxi, and Changzhou (i.e., the Su-Xi-Chang area or “SXC area”) in Jiangsu Province, China. The appearance of these fissures is closely associated with groundwater withdrawal both temporally and spatially. Based on field investigations, three models of the earth fissures in the SXC area were conceptualized. The changes in and distributions of normal and shear stress in hydrostratigraphic units due to groundwater extraction were analyzed numerically for each conceptualized model. Results from these numerical simulations indicated that geological conditions play a crucial role in the occurrence and distribution of earth fissures. Earth fissures are much more likely to initiate in areas where the depth of the bedrock below the ground surface is small, the thickness of the exploited aquifer unit changes abruptly, and the surface of the bedrock undulates dramatically. Earth fissures are also likely to occur in the vicinity of a distant restricted boundary. In addition, very stiff topsoil is more prone to cracking, and the locations of discharge wells also influence the occurrence of earth fissures.

Visco-elasto-plastic compaction of aquitards due to groundwater withdrawal in Shanghai, China

Long-term excessive groundwater withdrawal can cause aquifer systems to compact, and land subsidence ensues. The compaction of aquitards lags behind the change of groundwater level in adjacent aquifers, which is attributed to low hydraulic conductivity and great creep deformation of aquitards. Under the condition of groundwater withdrawal, aquitard clays may compact visco-elastically, elasto-plastically or visco-elasto-plastically, depending on the effective stress history they have experienced. Laboratory data manifest that aquitard clays have a similar constitutive relationship to aquifer sands, therefore the double-yielding visco-elasto-plastic mechanical model proposed for aquifer sands is applicable to aquitard clays. A fully coupled one-dimensional visco-elasto-plastic compaction model is constructed for aquitards to predict their compaction by integrating the double-yielding mechanical model with the flow governing equation of groundwater. The comprehensive compaction model not only makes the groundwater flow and soil deformation coupled, but also takes into account the complex deformation characteristics of aquitard units under long-term groundwater withdrawal, such as creep and plastic deformation under reloading.

Groundwater-derived land subsidence in the North China Plain

Land subsidence usually bears strong relationship to abstraction of underground fluid. Land subsidence occurs commonly in the North China Plain (NCP) and has become a major environmental factor hindering regional sustainable development. This paper focuses on issues associated with mechanism of land subsidence in the NCP. The analysis shows that multi-layer aquifer systems with deep confined aquifers and the thick normally consolidated or unconsolidated compressible clay layers are the key of geological and hydrogeological conditions favorable for the development of land subsidence in the NCP. Groundwater withdrawal results in an increase in the distribution of effective stress within the strata and the compression of the aquifers and the confining layers, and then triggers land subsidence. In the middle-east plain of the NCP, the land subsidence volume approximately represents the amount of water released from compression of deep aquifers and aquitards in that land subsidence is primarily caused by excessive groundwater withdrawal in deep aquifer system. The percentage of water released from compression of aquifers and aquitards in deep groundwater abstraction is significant but distinct in Cangzhou City and in the whole middle-east plain. This is due to the difference in local lithological structure and recharge and discharge conditions of deep groundwater system. The hysteresis of land subsidence is also discussed in typical areas and the results reveal that the time for completing the primary consolidation ranges from less than one year to tens of years, and that the rate of secondary compression tends to increase with the moisture content.

Optimal integrated management of groundwater resources and irrigated agriculture in arid coastal regions

Abstract. Groundwater systems in arid coastal regions are particularly at risk due to limited potential for groundwater replenishment and increasing water demand, caused by a continuously growing population. For ensuring a sustainable management of those regions, we developed a new simulation-based integrated water management system. The management system unites process modelling with artificial intelligence tools and evolutionary optimisation techniques for managing both water quality and water quantity of a strongly coupled groundwater–agriculture system. Due to the large number of decision variables, a decomposition approach is applied to separate the original large optimisation problem into smaller, independent optimisation problems which finally allow for faster and more reliable solutions. It consists of an analytical inner optimisation loop to achieve a most profitable agricultural production for a given amount of water and an outer simulation-based optimisation loop to find the optimal groundwater abstraction pattern. Thereby, the behaviour of farms is described by crop-water-production functions and the aquifer response, including the seawater interface, is simulated by an artificial neural network. The methodology is applied exemplarily for the south Batinah re-gion/Oman, which is affected by saltwater intrusion into a coastal aquifer system due to excessive groundwater withdrawal for irrigated agriculture. Due to contradicting objectives like profit-oriented agriculture vs aquifer sustainability, a multi-objective optimisation is performed which can provide sustainable solutions for water and agricultural management over long-term periods at farm and regional scales in respect of water resources, environment, and socio-economic development.

Study of impact on surface water and groundwater around flow fields due to changes in river stage using groundwater modeling system

Excessive ground water withdrawal can lead to ground water depletion, and this may have serious social and economic consequences. Attempts to limit groundwater pumping have been commonly based on the concept of safe yield. In this study, in order to evaluate safe yield, short- and long-duration pumping tests have been performed at four different sites (Purulia District, India) on Damodar River bed. The lithological survey was carried out along the river bed at regular intervals from 500 m to 10.5 km, covering a total stretch of 10-km up-stream and 0.5-km down-stream, to determine the soil profile and other soil characteristics. The points, where the maximum depth of porous medium was obtained, were selected for carrying out the pumping yield tests. The appropriate hydrogeologic approaches were employed to estimate the values of aquifer parameters, viz., specific yield (S y), transmissivity(T), and hydraulic conductivity (K) for the aforesaid sites under study, which were found to be in the range of 0.043–0.175, 2082–3983, and 219–603 m/day, respectively. A hypothetical aquifer-stream water interaction system has been developed using GMS software (groundwater modeling system) not only to represent the hydraulic head fluctuations in the groundwater system around well fields but also to quantify the flow rate due to change in river stage, recharge due to rainfall, and also to determine how the surface water could affect groundwater due to pumping.

Long-Term Land Subsidence Monitoring of Beijing (China) Using the Small Baseline Subset (SBAS) Technique

Advanced techniques of multi-temporal InSAR (MT-InSAR) represent a valuable tool in ground subsidence studies allowing remote investigation of the behavior of mass movements in long time intervals by using large datasets of SAR images covering the same area and acquired at different epochs. Beijing is susceptible to subsidence, producing undesirable environmental impacts and affecting dense population. Excessive groundwater withdrawal is thought to be the primary cause of land subsidence, and rapid urbanization and economic development, mass construction of skyscrapers, highways and underground engineering facilities (e.g., subway) are also contributing factors. In this paper, a spatial–temporal analysis of the land subsidence in Beijing was performed using one of the MT-InSAR techniques, referred to as Small Baseline Subset (SBAS). This technique allows monitoring the temporal evolution of a deformation phenomenon, via the generation of mean deformation velocity maps and displacement time series from a data set of acquired SAR images. 52 C-band ENVISAT ASAR images acquired from June 2003 to August 2010 were used to produce a linear deformation rate map and to derive time series of ground deformation. The results show that there are three large subsidence funnels within this study area, which separately located in Balizhuang-Dajiaoting in Chaoyang district, Wangjing-Laiguangying Chaoyang district, Gaoliying Shunyi district. The maximum settlement center is Wangsiying-Tongzhou along the Beijing express; the subsidence velocity exceeds 110 mm/y in the LOS direction. In particular, we compared the achieved results with leveling measurements that are assumed as reference. The estimated long-term subsidence results obtained by SBAS approach agree well with the development of the over-exploitation of ground water, indicating that SBAS techniques is adequate for the retrieval of land subsidence in Beijing from multi-temporal SAR data.

Estimation of spatial distrubition of groundwater level and risky areas of seawater intrusion on the coastal region in Çarşamba Plain, Turkey, using different interpolation methods.

Groundwater level plays a significant role in coastal plains. Heavy pumping and excessive use of near-coast groundwater can increase the intrusion of seawater into the aquifers. In the present study, groundwater levels were measured at 59 groundwater wells at different times during pre- and post-irrigation seasons (April and September of the year 2012) in Çarşamba Plain, Turkey. To select the best method, two deterministic interpolation methods (inverse distance weighing (IDW) with the weights of 1, 2, and 3 and radial basis function (RBF) with spline with tension (SPT) and completely regularized spline (CRS)) and two stochastic methods (ordinary kriging (OK) with spherical, exponential, and Gaussian variograms) and cokriging (COK)) were compared and then the best interpolation method was used to evaluate the spatial distribution of groundwater levels in different seasons and seasonal changes. A total of nine different techniques were tested. Also, risky areas of seawater intrusion in coastal area were determined using the best methods for two periods. The performance of these interpolation methods is evaluated by using a validation test method. Statistical indices of correlation (R (2)), mean absolute error (MAE), and root-mean-square error (RMSE) were used to select and validate the best methods. Comparisons between predicted and observed values indicated RBF as the optimal method for groundwater level estimation in April and September. When the best method RBF and the worst method IDW were compared, significant differences were observed in the spatial distribution of groundwater. Results of the study also revealed that excessive groundwater withdrawals during the post-irrigation season dropped the groundwater levels up to 2.0m in some sections. With regard to seawater intrusion, 9,103ha of land area was determined to be highly risky and risky.

A coastal groundwater management model with Indian case study

The complexity of the hydrogeological setup in coastal areas calls for the adoption of scientific groundwater management techniques. Excessive withdrawal of groundwater in coastal zones will lead to depression of the water table, with associated hazards such as putting the well out of use, rendering abstraction uneconomic with increased lift. A sustained regional groundwater drawdown below sea level runs the risk of saline water intrusion, even for confined coastal aquifers. Uncontrolled groundwater development may lead to reversal of the freshwater gradient, thereby resulting in saline water ingress into coastal aquifers. There are, however, several established methodologies to control and minimise the problems associated with groundwater extraction followed by saline water intrusion. This study developed a convenient and easily implementable analytical model for coastal groundwater management aimed at the control of saltwater intrusion. The technique includes withdrawal of coastal freshwater by means of qanat-well structures associated with artificial recharge through rainwater harvesting aided by percolation ponds and recharge wells. The proposed methodology is suitable specifically for not highly urbanised coastal areas with significant annual precipitation, good hydraulic conductivity of the aquifer and a low depth of fresh groundwater. As a case study, the model is applied to a coastal zone of the Purba Medinipur district of West Bengal, India. Adequate quantifications of the efficiency of the methodology are incorporated and relevant conclusions are drawn.

Time-series analysis of subsidence associated with rapid urbanization in Shanghai, China measured with SBAS InSAR method

River delta plains (deltas) are susceptible to subsidence producing undesirable environmental impact and affecting dense population. The City of Shanghai, located in the easternmost of Yangtze Delta in China, is one of the most developed regions in China that experiences the greatest land subsidence. Excessive groundwater withdrawal is thought to be the primary cause of the land subsidence, but rapid urbanization and economic development, mass construction of skyscrapers, metro lines and highways are also contributing factors. In this paper, a spatial–temporal analysis of the land subsidence in Shanghai was performed with the help of the Small Baseline Subset Interferometric Synthetic Aperture Radar. Twenty l-band ALOS PALSAR images acquired during 2007–2010 were used to produce a linear deformation rate map and to derive time series of ground deformation. The results show homogeneous subsidence within the research area, but exceptionally rapid subsidence around skyscrapers, along metro lines, elevated roads and highways was also observed. Because groundwater exploitation and rapid urbanization responsible for much of the subsidence in the Shanghai region are expected to continue, future subsidence monitoring is warranted.

Hydrogeological processes controlling the release of arsenic in parts of 24 Parganas district, West Bengal

A study was conducted to understand the hydrogeological processes dominating in the North 24 Parganas and South 24 Parganas based on representative 39 groundwater samples collected from selected area. The abundance of major ions was in the order of Ca2+ > Na+ > Mg2+ > K+ > Fe2+ for cations and HCO3 − > PO4 3− > Cl− > SO4 2− > NO3 − for anions. Piper trilinear diagram was plotted to understand the hydrochemical facies. Most of the samples are of Ca-HCO3 type. Based on conventional graphical plots for (Ca + Mg) vs. (SO4 + HCO3) and (Na + K) vs. Cl, it is interpreted that silicate weathering and ion exchange are the dominant processes within the study area. Previous studies have reported quartz, feldspar, illite, and chlorite clay minerals as the major mineral components obtained by the XRD analysis of sediments. Mineralogical investigations by SEM and EDX of aquifer materials have shown the occurrence of arsenic as coating on mineral grains in the silty clay as well as in the sandy layers. Excessive withdrawal of groundwater for irrigation and drinking purposes is responsible for fluctuation of the water table in the West Bengal. Aeration beneath the ground surface caused by fluctuation of the water table may lead to the formation of carbonic acid. Carbonic acid is responsible for the weathering of silicate minerals, and due to the formation of clay as a product of weathering, ion exchange also dominates in the area. These hydrogeological processes may be responsible for the release of arsenic into the groundwater of the study area, which is a part of North 24 Parganas and South 24 Parganas.

Hydrogeochemical features of groundwater of semi-confined coastal aquifer in Amol–Ghaemshahr plain, Mazandaran Province, Northern Iran

Hydrogeochemical data of groundwater from the semi-confined aquifer of a coastal two-tier aquifer in Amol-Ghaemshahr plain, Mazandaran Province, Northern Iran reveal salinization of the fresh groundwater (FGW). The saline groundwater zone is oriented at an angle to both Caspian Sea coastline and groundwater flow direction and extends inland from the coastline for more than 40 km. Spearman's rank correlation coefficient matrices, factor analysis data, and values of C ratio, chloro-alkaline indices, and Na(+)/Cl(-) molar ratio indicate that the ionic load in the FGW is derived essentially from carbonic acid-aided weathering of carbonates and aluminosilicate minerals, relict connate saline water, and ion exchange reactions. Saline groundwater samples (SGWS) (n = 20) can be classified into two groups. SGWS of group 1 (n = 17) represent the saline groundwater zone below the Caspian Sea level, and salinization is attributed essentially to (1) lateral intrusion of Caspian seawater as a consequence of (a) excessive withdrawal of groundwater from closely spaced bore wells located in the eastern part of the coastal zone and (b) imbalance between recharge and discharge of the two-tier aquifer and (2) upconing of paleobrine (interfaced with FGW) along deep wells. SGWS of this group contain, on average, 7.9% of saltwater, the composition of which is similar to that of Caspian seawater. SGWS of group 2 (n = 3) belong to the saline groundwater zone encountered above the Caspian Sea level, and salinization of the groundwater representing these samples is attributed to irrigation return flow (n = 2) and inflow of saline river water (n = 1).

Impact of Water Saving Technology On Blue Wateruse and Productivity: Analysis fron North Gujarat Region, India

North Gujarat is an absolutely water scarce region in Gujarat, though it contributes around 40 per cent of total groundwater draft in the state. Excessive withdrawal of groundwater for irrigation is leading to alarming drops in groundwater levels in many parts of the region. Since scope of supply side intervention is limited, it is imperative to manage irrigation water from demand side interventions aimed at to reducing its use. Overall objective of the present study was to analyse the impact of water saving technologies on applied water productivity. A study on experimental plot revealed that highest physical water productivity was found for castor under drip irrigation with plastic mulching as compared to flood irrigation followed by crop with organic mulching and lowest under drip irrigation. In case of groundnut, highest physical water productivity was obtained from the crop irrigated by easy drip method, whereas in case of sprinkler, highest physical water productivity was obtained from the micro-sprinkler. Potato crop was grown under drip and sprinkler methods of irrigation and highest physical water productivity was recorded from micro-sprinkler. From farmers’ field data, it was observed that farmers are using different types of water saving technologies for variety of crops. Before adoption of water saving technologies, on average blue water use for crop production was estimated to be 8397 m3 per hectare which was reduced to 5175.45 m3 per hectare after adoption of water saving technology, showing a decline of 61.6 per cent. Per hectare net income received by farmers before adoption of water saving technology was Rs 54615.46 and it increased to Rs 95759.41 after adoption of water saving technology. The variation in physical water productivity for same crop under different types of water saving technologies, suggested that government/promotional agencies should promote suitable water saving technology for different crops, which would help in achieving water saving and improvement in crop production and productivity.

Mechanical modeling of aquifer sands under long-term groundwater withdrawal

Long-term excessive groundwater withdrawal causes severe land subsidence and considerable economic loss. During the period of land subsidence, aquifer sands present complex deformation characteristics. Field data in the Southern Yangtse Delta, China have shown that the deformation characteristics of aquifer sands are closely related to the changing patterns of groundwater level the aquifer units have experienced. When the groundwater level fluctuates yearly within a certain range, the aquifer unit behaves primarily as an elastic material. When the groundwater level rises and falls alternatively with the average decreasing but higher than the previous lowest value the unit has experienced, the aquifer unit behaves primarily as a visco-elastic and elasto-plastic material. However, when the average level decreases and is lower than the previous lowest value the unit has experienced, the aquifer unit behaves primarily as a visco-elastic, elasto-plastic, and visco-plastic material. The plastic and creep deformation of aquifer sands is also proved through laboratory tests. With the increasing cycle number of loading, the creep and plastic deformation decreases and the expansion under unloading is closer to the compression under loading in a single cycle. On the basis of field and laboratory data, a new mechanical model is constructed, which can describe various kinds of deformation characteristics under different changing patterns of groundwater level, including elastic, visco-elastic, plastic, and visco-plastic deformation. The model includes two yielding stresses and six parameters. When the appropriate field data are available, the six parameters of the model can be determined through graphic methods. Then the deformation of aquifer units can be calculated if the changing groundwater level is known.

Regional land subsidence model embodying complex deformation

Large regions of land subsidence usually present very complicated historical deformation characteristics of sedimentary layers. A regional land subsidence model based on the modified Merchant model is developed and proposed to describe the visco-elastic-plastic deformation. Regional land subsidence models describing elastic, visco-elastic and elastic-plastic deformations can be derived from the one based on the modified Merchant model by setting proper values of the parameters involved. A new numerical method, the multi-scale finite-element method, is used to model regional land subsidence problems. Land subsidence in Shanghai from 1986 to 1998 is simulated as a case study for the model proposed in this paper. The results show that the model is capable of describing land subsidence with complex deformation characteristics, and can represent the mechanism of land subsidence caused by excessive groundwater withdrawal relatively well. The method is shown to be a good numerical method that significantly reduces computing effort and obtains accurate results.

시추공 전기비저항 토모그래피를 이용한 비저항 영상화: 과잉취수에 의한 석회암 지반침하 지역 사례

석회암 공동이 발달한 도심지역에서 지하수위 하강에 수반되어 발생한 함몰형 지반침하의 원인 규명 및 공동의 분포 특성 파악을 위하여 시추공을 이용한 전기비저항 토모그래피탐사를 실시하였다. 이때 지하수 수리지질 특성을 파악하기 위하여 시추코아의 비저항 측정, 지하수위 측정 및 수리전도도 해석을 병행하였다. 연구 지역에서의 완만한 지하수위 분포 특성과 0.8-<TEX>$9.3{\times}10^{-4}\;cm/s$</TEX> 범위의 수리전도도 분포로 부터 연구지역의 수리지질 특성은 불균질성이 크지 않은 것으로 나타났다. 시추코아를 이용한 전기비저항 측정 결과 연구지역의 석회암은 파쇄가 많은 경우, 변질이 심한 경우 및 신선한 경우로 나눠지며, 전기비저항은 각각 103-161, 218-277 및 597-662 ohm-m의 범위로 나타났다. 시추결과 점토로 충전된 석회암 공동 지점은 토모그래피 탐사자료의 역산 결과 50 ohm-m 이하의 낮은 비저항으로 나타났으며, 각 시추공 간 비저항 영상 단면으로부터 연구지역 전체적으로 지표 하부 심도 약 10-20 m 구간까지 파쇄대 또는 석회암 공동 구간이 분포하는 것으로 나타났다. 또한 석회암 공동의 직경은 약 4-6 m 규모로, 대부분 점토질로 충전된 것으로 판단된다. Electrical resistivity tomography surveys using boreholes were applied to reveal the cause of a catastrophic land subsidence accompanied by the excessive groundwater withdrawal in urban karst area and to map the connectivity of disseminated cavities over the study area. In order to understand the hydrogeological characteristics, resistivity using exsitu core samples, groundwater level for five boreholes, and hydraulic conductivity using slug test were measured. The hydraulic conductivity variation ranging from 0.8 to <TEX>$9.3{\times}10^{-4}\;cm/s$</TEX> for five boreholes and a gentle slope of groundwater level indicated that there is no significant characteristics of hydraulic heterogeneity. Core samples of the lime-silicated rock were classified as three groups including cracked, weathered, and fresh and measured the resistivity values ranged from 103 to 161, 218 to 277, and 597 to 662 ohm-m, respectively. Drilling results that showed the cavity filled with clay materials and tomogram for this region indicated resistivity value lower than 50 ohm-m. From the inverted resistivity results for each section with five boreholes, cavity and fractured layer were distributed along the depth between 10 and 20 m overall area and cavities ranging from 4 to 6 m filled with clay materials.

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.