Ashim Das Gupta

Optimal crop planning model for an existing groundwater irrigation project in Thailand

Abstract A monthly irrigation planning model is formulated for determining the optimal cropping pattern and the groundwater abstraction requirement in an existing groundwater development project. Two objectives, maximisation of net economic benefit and maximisation of irrigated area, aspired to by both the irrigation authority and the individual farmers in the Sukhothai Groundwater Development Project in Thailand are considered. To account for uncertainty in water resources availability, the model is solved for three levels of reliability of rainfall and groundwater resources (80, 50 and 20%). The effects of deficit irrigation on the net benefit and cropping intensity as well as on the yield of crops are also assessed by considering three levels (no deficit, 25% deficit and 50% deficit) of water application to the crops. To select the best alternative plan, a multi-objective analysis is carried out using the Analytic Hierarchy Process considering the preference of the decision makers, including farmers and irrigation project managers. The selected decision makers in the Sukhothai Project collectively allocate almost half of the total weight to reliability (or risk) factors, while the remaining preference is almost equally divided between the two objectives listed above. On average, they seem to prefer the planning alternative corresponding to average (hydrologic) conditions and full irrigation without any deficit.

Application of GIS and crop growth models in estimating water productivity

Abstract Tighter competition in water use is projected in the future. As water demand increases, water related problems could happen along the way. Accordingly, issues on water availability and use could be crucial to study to search for ways and means on how to cope up with the present trend. Sound water management practices could play a key role to the solution of problems relating to water availability and use. Water use in agriculture is considered the highest among other water users because of the water intensive processes involved in it. Aside from the crop water requirements, water loss, which are not beneficial to crop processes can add a huge volume to the total water usage in agriculture. Base from this argument, there could be greater possibility to save water from agriculture, which can be used for other purposes thereafter. To explore this option, analysis at the crop level could be beneficial. However, the issue of scaling should be also considered because the knowledge on the field scale could not be generally true in the basin scale. The objective of the study was to apply crop growth simulation models coupled with geographic information system (GIS) to analyze water productivity, which is an indicator of water use efficiency, at the basin scale. The methodology was applied to Laoag River Basin in Ilocos Norte, Philippines to study water productivity in spatial and temporal dimensions. Three crops were considered in the analysis: rice, maize and peanut. Simulations were done for both existing and potential agricultural areas. The potential productions of the selected crops from October 1996–September 1997 were used as bases in determining water productivity for the three cropping seasons (CS) being considered in the study. Water-limited productions were simulated for each of the crops, for each of the CS in the basin. Moreover, a marginal productivity analysis was done to determine the potential of water for crop production in the basin. Subsequently, the significance of irrigation was emphasized in the analysis when availability of water, and the combination of water and nitrogen (N) are limiting, respectively. The results showed that the spatio-temporal analysis of water productivity could provide substantial information for water saving opportunities and, hence, strategies in irrigated agriculture.

Water Sector of Bangladesh in the Context of Integrated Water Resources Management: A Review

This paper presents the general concepts and elements of integrated water resources management and the status of their adoption in Bangladesh at the national level. It describes the situation of the country with respect to the duality in the seasonal pattern of rainfall, the geographic position and the topography, which are the main constraints to its socio-economic development. An assessment of the past management practices in water sector identifies hindrances in the implementation of integrated water resources management process. The paper concludes with recommendations for improved water management in the country.

Application of Mike Basin for Water Management Strategies in a Watershed

Abstract Modeling at the basin scale provides essential information to policy makers in their decisions on allocation of water resources in the basin. This paper describes the application of a basin scale simulation model, Mike Basin, to the Mun river basin located in northeastern Thailand. Monthly simulation was carried out based on the water availability and utilization using hydrological data from 1965 through 1997. Climatic analysis found high seasonal variation: wet season water availability is more than six times dry season availability. Event-based reliability calculations of irrigation and water supply systems of the basin indicated that the existing level of demand has reasonable wet season water availability, but limited dry season availability. Moreover, sensitivity analysis found 80 percent reliable cropping intensity in wet season and only 12 percent in dry season. A proper management approach developed from this analysis may provide a basis for a decision for policy makers in relation to the optimal allocation of water resources.

Regional management modeling of a complex groundwater system for land subsidence control

The three-dimensional groundwater flow model MODFLOW and the one-dimensional consolidation model are coupled and calibrated to simulate the piezometric levels and land subsidence in the complex multi-aquifer system of the lower Central Plain of Thailand. The mathematical models are calibrated against historical data for the period 1955–1990 by considerably updating the system conditions used by previous studies. The aquifer system responses to different pumping schemes are then predicted for the period 1991–2010. The modeling procedure is carried out in close consultation with the Department of Mineral Resources (DMR), Royal Thai Government. The conclusions of the study will allow the DMR to develop and implement updated groundwater management policies, land subsidence control strategies and action programs in the Bangkok Metropolitan Area.

Equity and efficiency issues in irrigation water distribution

Abstract Irrigation water distribution policy should be both efficient and equitable. In most irrigation projects water distribution, particularly during the dry period fails to achieve one objective while trying to improve another, especially in unlined canal projects with a high seepage rate. How to improve both is a complex task. A methodology for choosing an appropriate water distribution policy in public irrigation projects considering both objectives of equity and efficiency is described. Assorted water distribution policies are generated through an optimization model by varying the level of irrigation and the proportion of area of each field plot to be irrigated. Then a simulation model is employed to evaluate the consequences with respect to efficiency and equity measures. Finally a multi-objective analysis is carried out to select a compromise solution. This methodology is applied to select a water distribution policy for irrigating wheat in a case study project.

Challenges for Sustainable Management of Groundwater Use in Bangkok, Thailand

An overview of groundwater development in Bangkok, Thailand, is provided and the paper highlights the environmental consequences of unplanned large-scale groundwater utilization. The effectiveness of the control measures adopted so far to address the issue of land subsidence is discussed. Recent initiatives and studies are analysed and the impediments to effective implementation of control measures are identified. Challenges faced by the Department of Groundwater Resources, which is responsible for groundwater development and management, are indicated. Recommendations are then put forward for improvement of the groundwater management system.

Simulation of infiltration from porous clay pipe in subsurface irrigation

Abstract Advances in the traditional method of subsurface porous clay pipe irrigation rely on knowledge of the distribution of water in the soil. Knowing the relationships among the hydraulic and physical parameters in the system is important for both the design and management of the system. To simulate the infiltration from the porous clay pipe and predict the wetted zone geometry in the soil, a computer model is developed herein. Laboratory experiments were conducted on soil samples representing two different soil textures in a specially designed bin to understand the flow phenomenon and to validate the developed model. In a given soil texture, the installation depth of the pipe and the volume of water applied in the soil are the major factors affecting the wetted zone. The relationships among various parameters, namely lateral spacing, installation depth, irrigation run time, hydraulic conductivity of the body of the pipe, and hydraulic head in the system, were established using the developed model.

Evaluation of the Effectiveness of Water Management Policies in Bangladesh

Water resources development and management policies initiatives in Bangladesh are primarily driven by the need for sufficient food grain production for the countrys teeming population and curtailing the perennial flooding problems. It is therefore necessary to investigate whether or not these objectives are being met. The aim of this study is to evaluate the impacts of past water resources development and management strategies on agriculture, food security, flood management and socio-economic development in Bangladesh. The research is based on the historical data of the relevant parameters of the water resources management over the period 1947–2005. The outcomes of the study demonstrate that past policies and strategies of water development have resulted in significant irrigation expansion, especially through intensified groundwater utilization, which has helped to achieve the countrys primary objective of self-sufficiency in food production. However, the provision of safe drinking water and sanitation facilities still remains a challenge in the country. Similarly, the impact of the flood control policies was diverse with success mostly apparent with regard to protection against modest events, while catastrophic, extreme events still effectively defying answer.

Farmers' Perception of Water Management under Drought Conditions in the Upper Awash Basin, Ethiopia

A survey was conducted in the Upper Awash River Basin, Ethiopia, to assess agricultural water management practices adopted by the farmers under drought conditions. The results show that on average drought prevails in the area once every two years and causes damage to both crops and livestock. Consequently, under such drought conditions, the farming communities have adopted various coping strategies and important among them are the sale of labour and sale of livestock and their products. The survey results also reveal that farmers in the rainfed agriculture areas practise mainly contour bunding to mitigate drought impacts.