Assessing the impacts of climate change on dependable flow and potential irrigable area using the SWAT model. The case of Maasin River watershed in Laguna, Philippines

Abstract

Seasonal changes in rainfall and temperature brought about by climate change affect water resources availability for rice production areas. There are currently no published applications of the soil and water assessment tool (SWAT) model on quantified effects of climate variability on irrigation service areas for rice production. The study assessed the impacts of climate change on dependable flow and potential irrigable areas of the Maasin River in Laguna, Philippines. Projected variations of rainfall and temperature in 2020 and 2050 developed using PRECIS model based on special report on emission scenarios were employed. The SWAT model was then used to simulate stream flow for each climate change scenario, from which dependable flows were quantified using flow duration analysis. Diversion water requirements for the rice areas in the watershed were determined using CROPWAT. Based on dependable flows and irrigation demand, the potential irrigable areas were estimated. Calibration and validation of the SWAT model showed satisfactory performance in stream flow simulations. The dependable flow in irrigation systems may decline by more than 50% in 2020 and by as much as 97% in 2050, because of seasonal changes in rainfall. In effect, the potential irrigable area may decrease to less than half of the current service area depending on the level of greenhouse gases emissions. SWAT water balance projections suggest surface runoff during wet seasons and increase annual groundwater recharge are possible sources of supplemental irrigation. Provisions of suitable storage reservoir facilities and groundwater development projects will alleviate water scarce conditions. The study demonstrated a technique that may be applied in other irrigation systems in the Philippines and in other countries to quantify the effects of climate change on dependable flows and potential irrigable areas. It can serve as an input to water resources planning and policy recommendations for climate change adaptation and risk reduction strategies. This technique can also be used to assess water resources in other perennial rivers and its viability for the development of new irrigation systems in the Philippines.

Modeling climate change impact on the inflow of the Magat reservoir using the Soil and Water Assessment Tool (SWAT) model for dam management

“…Other local SWAT studies focused solely on land use change impact assessments and streamflow changes (Araza et al 2021). Similarly, Alejo (2019) satisfactorily calibrated and validated a SWAT model in the Maasin River Watershed in Laguna, Philippines using actual streamflow. Reyes (2017) also applied the SWAT Model to predict streamflow and sedimentation in Wahig-Inabanga Watershed, Bohol, Philippines.…”

“…The majority of these researchers in the Philippines have studied the ability of the SWAT model for streamflow estimates. For example, Alejo & Ella (2019), used SWAT for streamflow estimates for irrigable area determination and Araza et al (2021) for river flow analysis. Other local SWAT studies focused solely on land use change impact assessments and streamflow changes (Araza et al 2021).…”

Two decades of rice research in Indonesia and the Philippines: A systematic review and research agenda for the social sciences

“…The University of the Philippines System, with rice scholars affiliated with their campuses in Los Baños, Diliman, Mindanao, and Manila, produced the next largest number of papers (more than 200 or 10%) on topics about rice pests and parasites (Horgan et al, 2019(Horgan et al, , 2021Vu et al, 2018), weed control (Awan et al, 2014(Awan et al, , 2015Fabro and Varca, 2012), and climate change impacts on rice farming (Alejo and Ella, 2019;Ducusin et al, 2019;Gata et al, 2020). Social studies of rice conducted by the University of the Philippines researchers include indigenous knowledge on climate risk management (Ruzol et al, 2020(Ruzol et al, , 2021, management options in extreme weather events (Lopez and Mendoza, 2004), agroecosystem change (Aguilar et al, 2021;Neyra-Cabatac et al, 2012), and the development and change over time of rice production landscapes (Santiago and Buot, 2018;Tekken et al, 2017).…”

Mekong River Delta Agricultural Mechanization Development: Case Study in Vinh Long Province, Viet Nam

“…Agricultural production contributes to around 38% of the GDP of the province [4]. Two of these rivers play an important role in supplying fresh water for agriculture production development in the province and in the MRD so appropriated irrigation system is one of the critical points for the agriculture sector and adapt with the climate change [5][6][7][8].…”