Changes in Irrigation Planning and Development Parameters Due to Climate Change

Considering changes in irrigation planning and development due to climate change is necessary to avoid system failure. This study demonstrated that changes in dependable flow and diversion water requirements in the future due to climate change will reduce potential irrigable areas. Climate change were based on the published projected climate in the study area. The dependable flow derived from successfully calibrated and validated Soil and Water Assessment Tool (SWAT) model streamflow simulations and the diversion water requirements based on the CROPWAT estimations of irrigation scheme were used to assess the potential irrigable areas. Substantial reductions in potential rice production areas (-4% to - 39%) were largely due to dwindled dependable flow (-1% to -25%) and an increase in diversion water requirement (+ 7% to + 26%). Reduction in potential irrigable area was projected during dry and normal years and may worsen towards the late twenty-first century under the worst-case climate scenario. Swelling of rivers during wet years will increase stream flows and potential irrigable areas but may also pose a danger of flooding. The development of water storage structures is necessary to reduce the adverse impacts of too much water during the wet years. Crop calendars should also be retrofitted to optimize the use of available rainfall during dry and normal years and climate-proof future irrigation systems. The results showed that it is necessary to incorporate climate change in irrigation planning and development. The methodologies described here could be used to climate-proof future irrigation systems in other areas in the Philippines and other countries.