Assessing Climate Change Impact and Water Resources Adaptation Measures of the Taoyuan Tableland in Taiwan

    The Taoyuan Tableland has faced a significant shortage of water resources due to booming socio-economic development in the past decades. The Shihmen Reservoir built in 1964 has been gradually unable to support the Taoyuan Tableland's agricultural and public water demands. By analyzing 1995-2014 rainfall data with the 3-month Standardized Precipitation Index (SPI-III), seven extreme meteorology drought events with the SPI-III less than -2 were found. Using the 0.05° statistically downscaled daily rainfall data provided by the Taiwan Climate Change Projection and Information Platform Project (TCCIP), it is expected to have 40 extreme meteorology drought events in 2041-2060. More drought events in the changing climate will further worsen the water shortage. It is urgent to develop adaptation measures for water resources management to enhance the climatic resilience of the Taoyuan Tableland. Agricultural ponds have been used for temporary water storage to support irrigation for more than 70 years, even earlier than the construction of the Shihmen Reservoir. Deepening agricultural ponds to provide distributed water storage capacity over the tableland is considered one of the effective adaptation measures to reduce the impacts of drought. This study focuses on how to systematically integrate and enhance the capacities of agricultural ponds to achieve a better climate-resilient Taoyuan Tableland.    Components of the Taoyuan Tableland’s water supply-demand system, including the Shihmen reservoir, agricultural ponds, agricultural districts, and water treatment plants, were integrated to build a water-resource system-dynamic model (WRSDM). Baseline (1995-2014) and SSP5-8.5 projections of 2041-2060 were obtained from the TCCIP. The Taiwan Water Resources Assessment Program to Climate Change (TaiWAP) was used to simulate flow discharges for running the WRSDM. The Deficit Percent Day (DPD) index and the Total Agricultural Deficit (TDAg) index are used to evaluate public and agricultural water shortages, respectively. The availability indicator calculated as the ratio of the average time without water shortage to the summation of average time without water shortage and average time of water shortage is used to represent the mean duration of no water shortage in the water resources system. Compared to the baseline (1995-2014), the average TDAg will increase by 10.25% and the availability indicator of public water will decrease by 21.51% due to more drought events in the mid-future (2041-2060). By deepening agricultural ponds by 2 meters, the availability indicator of public water will increase by 0.42% in the mid-future which is better than the case without applying any adaptation measure and indicates water shortage impacts to the domestic and industry sectors can be reduced. In addition to deepening agricultural ponds, different adaptation measures (e.g., rotated irrigation schedules, dry farming, reclaimed water, etc.) will be assessed to provide an optimized combination for adaptation policy recommendations in our future studies.