Study on the Application of Heterogeneous Measurement-Error-Filtered Kriging for Setting Groundwater Priority Management Zones in Yunlin Land Subsidence Area

The Yunlin-Changhua area is facing severe land subsidence. The reduction of groundwater pumping and the regulation of pumping wells are crucial tasks for preventing the deterioration of land subsidence. However, implementing comprehensive pumping reduction is challenging due to the close relationship between groundwater use and local industries. Considering the limited water supply and the need to minimize the impact on local industries, determining critical zones for groundwater extraction poses a challenge for the land subsidence prevention in Yunlin. Agriculture is the largest groundwater user in Yunlin. By using the Point Biserial Correlation method, this study identified the wells that exhibit significant groundwater pumping activity during the first crop rice period (which occurs during the dry season). Based on the spatial distribution of pumping volume from the selected wells, we established the prioritized zones for management. However, the spatial distribution of pumping volumes is susceptible to be outliers. Although using grid-based summing of pumping volumes helps mitigate the influence of outliers, the choice of grid size affects the level of detail in the distribution and may result in fragmented patterns that make it difficult to identify trends. To address these challenges, this study applies Heterogeneous Measurement-Error-Filtered Kriging to estimate pumping volumes and obtain smoothed distributions that facilitate the identification of concentration areas. The southern region of Yuanchang Township and the central area of Shuilin Township in Yunlin were identified as areas with the highest pumping activities. Considering subsidence characteristics, it is recommended that Yuanchang Township be designated as the priority management zone for groundwater. Any water shortages in this priority area may be alleviated through the water supply from neighboring areas or by making changes in land use to reduce groundwater consumption. The suggested priority groundwater management zones can effectively reduce management costs.