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Characteristics
Malaysia Water Research Journal
Value
Annual Precipitation (mm) 2500
Channel Slope 1 : 204
Mean Temperature (⁰C) 27
Land Elevation (m)
0 to 500 m
Under current usage, Skudai Watershed is divided into pervious and
impervious land segments. Pervious and impervious land segments consist of
forestland (3.83%), agricultural land (39.76%), urban/residential land (52.46%) and
barren land (3.96%).
THEORY AND CALCULATION
HSPF is a comprehensive water quality model that is able to simulate complex
hydrological processes in comparison to simple method used in Export Coefficient
Models. HSPF is designed with three different routines which are Pervious Land
Segments (PERLND), Impervious Land Segments (IMPLND) and Reach Segment
Operations (RCHRES). In HSPF, PERLND is the module that simulates the water
quality and quantity processes which occur on a pervious land segment. The
primary module sections in PERLND simulate snow accumulation and melt,
water budget, sediment produced by land surface erosion and water quality
constituents by various methods. Modules in IMPLND are similar to the PERLND
module. However, the IMPLND sections are less complex, since they contain
no infiltration function and consequently no subsurface flows. The operation
module used to simulate Channel Reaches (referred to as RCHRES in the HSPF
model) contains separate sections of code to simulate hydraulic behavior, pH,
temperature and other water quality related processes. HSPF/BASINS used spatial
variability of Skudai watershed to divide the basin into many hydrologically
homogeneous land segments and simulating runoff for each segments
independently. The HSPF needs precipitation, temperature and estimation of
potential evapotranspiration input data to perform hydrologic simulation. Hourly
precipitation and temperature input data were collected from Senai International
Airport monitored by Malaysian Meteorological Department (MMD). Input data
for potential evapotranspiration were estimated using maximum and minimum
hourly temperature using Hamon PET equation (P. Hummel et al.,2001). These
input data were disaggregated into hourly input data since the hydrological
simulation was done using hourly time step.
The HSPF model for the Skudai Watershed were calibrated from 5/11/2013
to 5/2/2014 and then validated from1/3/2012 to 15/5/2012. The watershed
model was calibrated and validated at Department of Irrigation and Drainage
Malaysia (DID) gauge station at Kampung Pertanian, Kulai Johor. The flow data
was obtained from rating curve and from Automatic Global (WL16) Water Level
Data Logger (Global Water, 2014) at Kampung Pertanian. The Rating Curve
Institut Penyelidikan Hidraulik Kebangsaan Malaysia (NAHRIM)
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National Hydraulic Institute of Malaysia (NAHRIM)