Abstract
Abstract. Cebu, with its growing development and increasing demand for water, needs tools and inputs to efficiently understand and manage its water resources. Rainfall runoff models were developed to model surface runoff which may be used to assess water availability. Soil Conservation System (SCS) Runoff Curve Number (CN) method predicts runoff based on an empirical curve number for ungauged watersheds. This study aims to estimate the amount of runoff for the catchments of Cebu Island using the SCS-CN Runoff technique. The data needed for the application of the method in this study were rainfall distribution data, land use/land cover and soil texture for curve number assignment, LiDAR DEM for the delineation of the catchments, and supporting runoff measurements from a different runoff estimation model for assessment of the results. The collected data were prepared by assigning the mean statistics of the rainfall distribution and the composite curve number for each catchment using Geographic Information System (GIS). The calculation of the runoff was also done using the same framework. Maps representing Cebu Island’s catchments’ runoff estimates were produced. Since observed runoff data were unavailable, the results were verified by comparing the SCS-CN estimated runoff to the results of a physically-based distributed hydrologic and hydraulics modelling software, FLO-2D. The SCS-CN estimations were found to coincide with the FLO-2D runoff estimates based on various statistical assessments. Although the results may have higher uncertainties due to the unavailability of observed runoff data, the SCS-CN Runoff method provided relevant results to that of a complex simulation model. Thus, the method may be applied to estimate runoff of ungauged catchments of Cebu Island, the results of which could provide relevant information for water resource management.
Highlights
1.1 Background of the StudyCebu is known as an international commercial and business hub, with its capital, Cebu City as the second largest metropolis in the country
This chapter discusses the process of data preprocessing and the computation of runoff estimates for the catchments of Cebu Island using Soil Conservation Service (SCS)-Curve Number (CN) Runoff method in Arcmap 10.1
The catchments were delineated from a 10-meter resolution Light Detection and Ranging (LiDAR) Digital Terrain Model (DTM) using a watershed delineation framework compiled by Al Duncan, a UK Geomatics Specialist
Summary
Cebu is known as an international commercial and business hub, with its capital, Cebu City as the second largest metropolis in the country. Different hydrological modelling systems that incorporates the SCS-CN method for the computation of precipitation loss and the empirical characterization of the soil and ground cover properties have been adapted to: evaluate water resources resiliency (Marteleira et al, 2018); to determine land cover change impacts to water supply (Caja et al, 2018); and to assess the hydrologic behaviour of a watershed in response to climate and land cover changes (Arceo et al, 2018) in the Philippines. The studies for the precipitation loss and excess computations and the runoff property characterizations through the SCS-CN method in the Philippines were incorporated in semi-distributed and distributed physically based models These types of models commonly require multiple parameters and observed measurements for calibration which are usually unavailable and requires extensive time and manpower to collect (Sitterson, et al, 2017). This chapter discusses the process of data preprocessing and the computation of runoff estimates for the catchments of Cebu Island using SCS-CN Runoff method in Arcmap 10.1
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