The study aims to assess the surface water resources potential of an ungauged catchment which is located at Barangay Nagsabaran, Diadi, Nueva Vizcaya. For this purpose, an interview was conducted to selected respondents, water quality was tested in the area, streamflow and water discharge was collected and surface runoff modelling was done with the Soil and Water Assessment Tool (SWAT) Model. It was identified through survey that the major source of water of the barangay comes from unprotected spring (59.8%) and stream, river (42.3%) that is utilized by the residents for their household (98.9%), business (22.4%), livestock (13.2%), farming (11.7%) and aquaculture (0.7%) activities. The water quality did not exceed the water quality guidelines promulgated by DENR except for color whose value ranges from 39 Color Unit to 63 Color Unit compared to 5 Color Unit during the period covered. This exceedance is associated with naturally dissolved organic matter. Water discharge from the waterpipes connected to Nagsabaran waterfalls is also has an average discharge of 0.08 Lps (0.00008 cu m/s) while, thestreamflow from the Nagsabaran waterfalls to the Oriwong creek was 0.069 cu m/s. The SWAT model extracted 14 subbasins with 177 Hydrologic Response Units (HRU's). There are eight parameters used in this study for which Soil Available Water Capacity (SOL AWC) is the most sensitive with p-value of 0.06 and 1-stat of -1.90. SWAT simulation have been done for the period 1997-2013. Calibration and simulation were done for the streamflow and the performance of the model is evaluated using two methods: the coefficient of determination (r²) and the Nash-Sutcliffe Simulation Efficiency (NSE) with an overall value of 0.5066 and -0.72, respectively. The, effective allocation of water resources requires knowledge of the area and sufficient data for use of watershed models to simulate the flow of water and the transport of sediments and other associated water quality constituents.

Keywords: surface water potential, water quality, hydrologic modelling, streamflow

Thesis (Master of Science in Agricultural Engineering - Soil and Water Management)

Includes appendices and bibliographical references.