A sustainable strategy for conjunctive water management must include information on the temporal and spatial availability of this natural resource. Because of water shortages in the dry seasons, farmers on the Upper Plain of the Chao Phraya River basin, Thailand, are increasingly using groundwater to meet their irrigation needs. To evaluate the possibilities of conjunctive water management in the area, the spatial-temporal changes in the water table of the Younger Terrace Aquifer were investigated. First, a regional geomorphological map based on field surveys, remote sensing and previous environmental studies was developed. Then, the well data were analyzed in relation to rainfall, streamflow, yield and pumpage, and the data were interpolated using geostatistical techniques. The results were analyzed via integrated zoning based on color theory as applied to multivariate visualization. The analysis results indicate areas that would be more suitable for groundwater extraction in a conjunctive management framework with regard to the natural hydrogeological processes and the effects of human interaction. The kriging results were compared with the geomorphological map, and the geomorphological areas exhibit distinct hydrogeological patterns. The western fans exhibit the best potential for the expansion of conjunctive use, whereas the borders of the northern fans exhibit the lowest potential.
Abstract. The Upper Central Plain of Thailand, where farmers depended on both surface water and groundwater. Water allocated from the Bhumibol and Sirikit Dams are limited and caused water shortage in the dry years. Most farmers turn to use groundwater to supplement irrigation water in the dry years. This study aims to understand the flow budget change of groundwater under climate change scenario. The conjunctive use ratio of surfaceas well as groundwater were investigated by field surveys and groundwater flow modeling, using the MODFLOW model to simulate the groundwater movement over the 10 years . The study used the bias-corrected MRI-GCM data to project the future climate conditions (during 2015 -2029 and 2075-2089) and assess the impact on flow budget change of groundwater system. The conjunctive use ratio were analyzed from surface water use and flow budget of groundwater system in term of water demand, rainfall, reservoir storage, groundwater recharge, groundwater storage, groundwater pumping. The study shows the flow budget change and conjunctive use ratio of each season and water year in the past and in the future under climate change scenarios.
The Phitsanulok Irrigation Project is located in the Nan Basin of the Upper Central Plain of Thailand where farmers depended on both surface water and groundwater. Land use and climate changes are the important factors to determine the runoff from the watershed. The changes also affected to runoff volume/pattern to the dam operation and may cause flood and drought situations in the downstream area. Sirikit Dam is one of the biggest dams in Thailand which cover about 25 % of the runoff into the Central Plain where the Bangkok Capital is located. Though there is the Sirikit Dams storing water to be used during dry period but water allocation is limited and still caused water shortage during dry season. The study aims to determine the role of groundwater to mitigate the drought situation from the past and to study the groundwater use for adaptation to climate change in The Phitsanulok Irrigation Development Project. In this study, the relationship of recharge rate with climate data was developed in terms of precipitation, evapotranspiration, temperature and soil type under monthly time series data and the study found that there were in good relationship. Groundwater will take an important role to alleviate from the water shortage situations in climate change conditions when compared with the situations based on the existing water use pattern. The limit of ground water to alleviate water shortage will be 80 and 77 MCM/year in average, in near future and far future periods to keep water table drawn down in the safe manner even when the Sirikit’s reservoir operation rule is improved.
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