By Alistina Shrestha
A study led by Julius Incillo Jimenez has demonstrated how integrating satellite data with hydrological models can significantly improve water resource management in climate-vulnerable regions. Jimenez, who is a recipient of a scholarship from the Philippines Department of Science and Technology (DOST), is a Dual Degree student in the Asian Institute of Technology (AIT) and Indian Institute of Technology Roorkee (IIT Roorkee) from the Remote Sensing and Geographic Information Systems (RSGIS) Program at AIT’s School of Engineering and Technology (SET).
The research published in Earth Science Informatics introduces a new approach to the management of agricultural water resources in the Padsan River Watershed (PRW) of Ilocos Norte in the Philippines. It integrates open-access satellite rainfall data with advanced modeling tools, bridging a critical gap between surface water (river discharge) and subsurface water (groundwater recharge), providing scientific insights and practical solutions for irrigation scheduling, groundwater conservation, and climate adaptation.
The Padsan River Watershed is home to over 350,000 people and more than 27,000 hectares of farmland. It is the largest agricultural basin in the province and a significant source of the country’s food supply. However, it suffers from alternating extremes of excess and scarcity, severe drought in dry seasons, and damaging floods during rainy seasons. These extremes are made worse by obsolete irrigation data and poor and fragmented governance. These challenges impact agricultural production and water governance, which also affects food security in Padang.
“Water security is food security,” Jimenez emphasizes. “Yet in many regions like Ilocos Norte, we still make irrigation decisions based on outdated or incomplete data.” Climate change is driving water shortages that threaten farms across Asia and the Pacific. Governance challenges are worsening the crisis, creating an urgent need for a smarter data-driven approach to water management.
The research, titled “Assessment of the Spatiotemporal Dynamics of River Discharge and Groundwater Recharge to Support Sustainable Water Management for Irrigated Agriculture in the Padsan River Watershed”, examined seasonal and regional water patterns in the Padsan River Watershed. It also explored ways to use water more sustainably in a changing climate.
To achieve this, Jimenez employed the Soil and Water Assessment Tool (SWAT), which was calibrated for use with bias-corrected CHIRPS satellite-based rainfall data from 1989 to 2021, to generate simulations to understand hydrology over 32 years. This process was done in four phases:
- Data Acquisition – Satellite and ground data, including CHIRPS, SRTM-DEM, PAGASA meteorological data, and NIA river discharge records (2003–2021), were gathered.
- Bias Correction – CHIRPS data were corrected using the Quantile Mapping (QM) method to improve rainfall simulation accuracy.
- Hydrologic Modeling – The SWAT model simulated 32 years (1989–2021) of hydrological behavior, focusing on River Discharge (RiverQ) and Groundwater Recharge (GWR).
- Calibration and Validation – The model was calibrated using the SUFI-2 algorithm via SWAT-CUP, validated against observed discharge data, and assessed using NSE, R², RMSE, PBIAS, and KGE.
A key innovation was successfully coupling corrected CHIRPS data with SWAT in a data-scarce region. This allowed detailed simulations of water behavior in the watershed.
The study found that:
- Average annual river discharge: 595.20 m³/s
- Average annual groundwater recharge: 427.18 mm
- Agricultural lands recorded the lowest recharge rates, indicating risks of groundwater over-extraction and potential land subsidence.
The results highlighted significant seasonal and regional differences in water availability. It emphasized the need for targeted irrigation schedules, efficient water allocation, and long-term groundwater management policies.
The study’s results have been shared with local agencies, including the National Irrigation Administration (NIA) and the Ilocos Norte Water District. They are already applied in:
- Feasibility studies for new irrigation infrastructure
- Policy guidance for Managed Aquifer Recharge (MAR)
- Water allocation schedules for dry-season cropping
- Flood and drought risk mapping for local governance
“This research provides the missing link between planning and precision,” said Prof. Nitin Kumar Tripathi, Jimenez’s co-advisor. “It’s a tool that governments can use.”
Jimenez’s connection to the research goes back to his childhood in Ilocos Norte. “I remember farmers praying for rain, while floodwaters had just devastated the rice fields a few months before. The mismatch haunted me,” he recalls. This experience inspired him to move from a background in education and social development to geospatial hydrology, combining satellite science, climate modeling, and environmental engineering.
“My path into hydrological modeling wasn’t a straight line,” he says with a smile. Starting in social science, he later pivoted to climate modeling, GIS, and environmental engineering. “I deviated because I felt that understanding water deeply and technically was the key to solving so many of our social challenges.”
His academic detour has led to multiple fellowships, publications, and now, a model that’s ready for use by watershed planners across the Philippines and beyond. “I realized that technology doesn’t replace people, it empowers them,” he said.
His unique dual-doctorate journey between AIT and IIT Roorkee allowed him to integrate perspectives from Southeast and South Asia, creating a comprehensive research framework that connects tropical hydrology, satellite science, and policy translation.
The research aligns with five core Sustainable Development Goals: SDG 2 – Zero Hunger, SDG 6 – Clean Water and Sanitation, SDG 13 – Climate Action, SDG 15 – Life on Land, and SDG 17 – Partnerships for the Goals. The study demonstrates that even in the face of data scarcity and institutional fragmentation, science-driven governance is possible. By making the invisible visible, literally mapping the recharge beneath our feet, Jimenez’s research lights supports the path toward resilient, equitable, and climate-smart agriculture.
