Groundwater management for Lower Indus Basin
Introduction
The authors have proposed a two level optimization model in their earlier paper Garg and Ali (1998) to obtain the optimal cropping pattern and the sowing dates. The model was applied to the Dadu Canal Command of the Lower Indus Basin. The coupling of groundwater hydraulics with canal water was not considered in the optimization model because it was found from the irrigation project reports (Harza Engineering International, 1991) that the canal water was always much cheaper (actual operation and maintenance cost) than the tubewell water for the Lower Indus Basin. However, the interaction between surface water and groundwater was considered in the model by imposing a groundwater balance constraint on the groundwater withdrawals. Monthly optimal canal and groundwater withdrawals were also obtained by Garg and Ali (1998). However, no policy for the optimal groundwater withdrawal was determined based on groundwater hydraulics. The present paper aims to find out the optimal pumping rates and the regional changes in hydraulic heads caused by the optimal groundwater withdrawals from the aquifer.
Section snippets
Previous work
Burt (1967) has developed an economic model for allocation of groundwater. The economic consequences of altering various parameters in the model were examined with respect to the effect on the groundwater equilibrium and rate of pumping. Gisser and Sanchez (1980) have discussed the problem of groundwater pumping. They conducted an analytical comparision between a free market behaviour (no control) and optimal control and shown that if the storage capacity of the aquifer is relatively large then
Formulation of groundwater simulation model
The finite element method is used to solve the Boussinesq equation by Galerkin weighted residual criteria. Shape functions are used to approximate the spatial distribution of the variables and the finite difference has been used to approximate the temporal distribution. Eight noded isoparametric elements are used for the domain subdivision. The resulting approximate equations have been solved by frontal solution technique.
The unconfined aquifer hydraulics are described by Boussinesq equation
Formulation of groundwater management model
An algebraic technological function (ATF) relates in a simple algebraic manner the draw down to the pumping stress, which is the behavior that stress produces in an aquifer. Groundwater and economic models can be tied together in a management model through the use of ATF. An ATF relating draw down in wells to the pumping was determined by Maddock (1972). The same concept has been used here.
The draw down at the pth well at the end of qth time period assuming pulse pumping, s(p,q) is given by the
Objective function
The objective function is to minimize the pumping cost which comprises of the variable energy cost and is function of the total lift (draw down plus initial lift), and rate of pumping. The objective function can be expressed as:In which M is the number of wells penetrating the aquifer; NT the number of pumping periods; L(p) the initial lift at pth well; s(p,q) the draw down at pth well at the end of qth time period and Q(p,q) the pumping at pth well during q
Application
The groundwater hydraulic management model has been applied to the Dadu Canal Command of the Lower Indus Basin. Aquifer testing undertaken during Lower Indus Project at 26 sites indicated that alluvial sediments constituted an aerially extensive, fairly homogeneous unconfined aquifer system.The Dadu Canal Command consists of 210 000 ha irrigated area underlain by homogeneous unconfined aquifer. Mean lateral hydraulic conductivity of the aquifer can be taken as 42 m/day and storage coefficient as
Groundwater management model
To assess the interfering effects on the optimal pumping rates, the groundwater management model is applied to a well field consisting of four wells, chosen arbitrarily from the Dadu Canal Command. Table 1 gives the monthly optimal water releases from different sources for the Dadu Canal Command, obtained from the two-level optimization model (Garg and Ali, 1998) corresponding to existing tubewell capacity of the command. The tubewell capacity is exhausted in peak months, giving an average
Groundwater simulation model
The simulation model has been applied to obtain the groundwater flow pattern for the pumping of optimal amount of groundwater. The monthly optimal groundwater withdrawals have been taken from the two level optimization model (Table 1). Optimal pumping rates are taken from the groundwater management model. The losses are taken to be the same as per the data given in Garg and Ali (1998). The water table contours have been obtained for each month considering the available groundwater recharge
Proposed groundwater development
It is clear from the Fig. 4 that the recharge is getting accumulated in the lower reaches over the years and is causing waterlogging problem. Hence, there is a necessity to increase the groundwater withdrawals. In order to estimate the increased groundwater withdrawals, Garg and Ali (1998) model was run on the same previous data but relaxing the limit on maximum groundwater withdrawals by tubewells. The groundwater withdrawals were allowed at the most equal to the annual groundwater recharge.
Conclusions
Groundwater management studies are carried out for the Dadu Canal Command aquifer of the Lower Indus Basin. It has been shown that the tubewells may be operated at their maximum capacities to pump the required volume of water to get an overall optimum management policy. The simulation model is applied to determine the waterlevel contours for the optimal pumping schedule. The groundwater level contours indicate a serious waterlogging problem in the lower reaches with the existing tubewell
Acknowledgements
The authors express their sincere thanks to Mr. Quamrul Hassan for helping in the preparation of this document.
References (18)
- et al.
Two level optimization model for Lower Indus Basin
Agric. Water Manage.
(1998) - et al.
Groundwater hydraulics in aquifer management
J. Hydraulic Div. ASCE
(1974) - et al.
Groundwater management with fixed charges
J. Water Resou. Planning Manage. Div. ASCE
(1980) Temporal allocation of groundwater
Water Resou. Res.
(1967)- Bear, J., 1979. Hydraulics of Groundwater. McGraw-Hill International Book Company, New...
- et al.
Optimal control model for groundwater management
J. Water Resou. Planning Manage. ASCE
(1986) - Chaturvedi, M.C., and Srivastava, V.K., 1979. Study of a induced groundwater recharge. Water Resou. Res. 15,...
- et al.
Competition verses optimal control in groundwater pumping
Water Resou. Res.
(1980) A review of distributed parameter groundwater management modeling methods
Water Resou. Res.
(1983)
Cited by (16)
Hydrological problems of water resources in irrigated agriculture: A management perspective
2016, Journal of HydrologyCitation Excerpt :The approach combines the use of groundwater flow simulation with optimization techniques to refine pumping strategies identified using flow simulation. Garg and Ali (2000) applied a model in Dadu Canal command of the lower Indus Basin, Pakistan, to address the problem of waterlogging. They concluded that waterlogging can be managed by operating the existing tubewells at their maximum capacity and installing additional tubewells at new locations.
Groundwater resources management through the applications of simulation modeling: A review
2014, Science of the Total EnvironmentCitation Excerpt :Water and salt are the key elements that decide the sustainability of irrigated agriculture in arid and semiarid ecosystems. Due to that, water and salt balance studies have been done at various research stations worldwide (Williams, 1987; Garg and Ali, 2000; Dai and Labadie, 2001; Upadhyaya and Chauhan, 2002; Oster and Wichelns, 2003; Tuteja et al., 2003). In arid and semiarid areas, provision of irrigation is vital to enhance crop production.
Simulation-optimization modeling for conjunctive water use management
2014, Agricultural Water ManagementIntegrated non-linear model for optimal cropping pattern and irrigation scheduling under deficit irrigation
2014, Agricultural Water ManagementCitation Excerpt :However the interaction between surface and ground water is considered by imposing a ground water balance constraint such that the annual ground water withdrawals cannot be more than the annual ground water recharge. A ground water management model can be separately worked out to keep the ground water levels within desirable limits as shown by Garg and Ali (2000). The NLP optimization model is solved by Microsoft Excel 2007 Solver.
The extent of waterlogging in the lower Indus Basin (Pakistan) - A modeling study of groundwater levels
2012, Journal of HydrologyCitation Excerpt :The situation is alarming and it not only warns to aptly utilize all the possible surface and groundwater resources but also to optimally manage, conserve, and use them (Garg and Ali, 1998). On other hand, the seepage losses from earthen irrigation network, poor irrigation application efficiency, and mismanagement of existing water resources have created the twin menace of waterlogging and salinity (Alam and Bhutta, 2004; Garg and Ali, 2000; Qureshi et al., 2008; Shah, 1988; Sufi et al., 1998). The flood of 2010 further aggravated the problem of waterlogging resulting in one fifth of the entire landmass (most of the fertile agricultural land on either side of the major rivers) was submerged (Mustafa and Wrathall, 2011).