This is possible through the Water Erosion Prediction Project (WEPP) model, whose applicability in the Philippines has been tested and demonstrated.
The model was developed by the National Soil Erosion Research Laboratory of the Agricultural Service, United States Department of Agriculture (USDA), Forest Service of the Bureau of Land Management, 10 universities in the US, and many international scientists.
It has been proven applicable in many continents, including Asia (particularly in China).
WEPP is a process-based, continuous computer simulation model for predicting water-induced soil erosion either on a hill slope or watershed scale. It consists of nine components, namely: climate generation, hydrology, soil physics, irrigation, plant growth, residue decomposition, hydraulics of overland flow, erosion, and even winter processes.
The traditional approach on erosion estimation in the Philippines uses the Universal Soil Loss Equation (USLE), which simulates erosion on a plot scale. WEPP can simulate or predict soil loss and sediment yield on a watershed scale. The WEPP model has addressed other limitations in USLE.
In the Philippines, Victor Ella of UP Los Baños tested and demonstrated WEPP’s applicability for estimating and predicting soil erosion and sediment yield in selected small upland watersheds of the Manupali River Basin in Bukidnon.
The study was monitored by the Philippine Council for Agriculture, Forestry and Natural Resources Research and Development (PCARRD).
Results showed that, among other things, when entire watershed is not cultivated and instead covered by small trees and grasses, the sediment yield amounts to only 1.9 tons per hectare per year.
If 20 percent of the watershed area is cultivated and planted to corn, sugarcane, vegetables, and grasses in between, sediment yield would increase to 11.1 t/ha per year.
However, if 50 percent of the watershed is cultivated and planted to the same set of crops, the sediment yield would increase to 19.9 t/ha per year.
"This implies that watershed managers, land-use planners, local government units, and other stakeholders may have to review or reformulate strategies for addressing soil erosion problems," the study stressed. – RAF