Assessment of Groundwater and Surface Water Use Efficiency (WUE) and Economic Water Productivity across Thailand Agricultural Sector through the Lens of Sustainability

Thailand’s water and climate adaptation are complex and under challenges from a low-lying delta capital city, combination of intensifying floods and droughts, increasing land subsidence, river and coastal erosion, biodiversity loss and sea-level rise.  Thailand’s approach to water development and management has always been relying on multiple sector basis without substantial consideration of any interactions between them and institutions and policies are typically flawed, in the long-term leading to inefficient water use and undesirable consequences from development, all are creating an urgent need for sustainable solutions, actions, and practices.  As climate change intensifies, growing water scarcity, unpredictability, and vulnerability drive the need for sound baseline economic analyses related to current water use efficiency and water productivity, providing the basis for innovative approaches to allocate water to various sectors and increase the efficient use of existing water supplies with minimal adverse effects, and setting the stage for more sustainable water management.    In this study, we assess the water use efficiency (WUE) and economic water productivity across Thailand agricultural sector to focus on the efficient use of water resources under water scarcity threat at the basin-level based on standardized terminologies and formulas from modified version of the FAO’s monitoring framework.  Meteorological, physical geospatial, Gross Provincial Products, and historical allocated surface water and groundwater to agricultural sectors in irrigated area data (based on the System of Environmental Economic Accounting for Water approach) are collected and the economic efficiency in agricultural sector expressed as a quantitative ratio between the amount of monetary production (i.e., value added in agricultural sector) per area as resources or efforts made for its realization are investigated.  With increasing in water allocated to dry-season irrigated area, slow rising in the economic efficiency of agricultural sector is observed.  Change in the economic water productivity defined as a ratio between the amount of monetary production per unit irrigated water resource made to obtain them (THB/m³), is further evaluated.  Declining in the economic water productivity is observed with increasing of dry-season allocated water, suggesting that the economic water activity is complex, requiring specific level of resource consumption to achieve the efficiency, not entirely corresponding to the allocated expenditure.  Dry-season water allocation escalates consistently with increase in annual rainfall and growing irrigated crop area, but fails to enhance both water economic productivity and sustainability.   Greater attention needs to be focused on managing surface water and groundwater for conjunctive use. We need a better understanding of biophysical and socio-economic changes in basins over time and improved measures of basin-level efficiencies before we can determine in a given situation the potential for increasing water productivity through responsive interventions and policies.  Decisions on basin-level allocations among sectors cannot be based strictly on economic efficiency but they must involve value judgements as to how best to benefit society inclusively as a whole. This will include setting priorities in the management of water resources to meet objectives such as ensuring sustainability, meeting food-security needs and providing the more vulnerable segments of society with access to water.