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CHAPTER III IMPACT OF LAND USE CHANGES ON WATER YIELD IN UPSTREAM
CISADANE WATERSHED USING HEC-HMS MODEL
3.1. Introduction
3.2.1. Background
Runoff is one of the most important hydrologic variables used in most of the water resources applications. Sound information on quantity and rate of runoff from
land surface into streams and rivers is vital for integrated water resource management. This information is needed in dealing with many watershed
development and management problems. Physically distributed hydrologic models for prediction of river discharge require considerable hydrological and
meteorological data. However, traditional data collection is expensive, error prone, time consuming and a difficult process. To alleviate this problem remote sensing
and geographic information systems geo-informatics are sound technologies. The use of hydrological modeling systems for water resources planning and
management is becoming increasingly popular. Since these hydrological models mostly deal with land phase of hydrological cycle, data related to topography and
physical parameters of watershed are a necessary pre-requisite for these models. Computer based geographic information system furnish this requirement
efficiently. These systems link land use data to topographic data and to other information related to geographic locations. When applied to hydrologic systems,
non-topographic information can include description of soils, land use, ground cover, ground water conditions, as well as man-made systems and their
characteristics on or below the land surface. Flow estimation at a point in a river is vital for a number of hydrologic
applications including flood forecasting, water resource management, and for development applications. This chapter presents the result of a watershed scale
rainfall-runoff modeling on gaged part of Upstream Cisadane Watershed using the hydrologic model in a GIS environment. The watersheds were modeled using HEC-
44 HMS 3.5. Datasets used in the analysis were created using Arc Hydro Tools and
HEC-GeoHMS 5.0. both are ArcGIS extensions. The model framework developed in the study considered the spatial variation
in the runoff response of the watershed through the use of curve numbers based on soil type and land use, and the spatial distribution of the rainfall in the watershed
by using rainfall data from a number of rain gage stations located in different parts of the basin.
3.2.2. Objective
To assess the impact of the predicted land use changes on water yield using hydrology model HEC-HMS.
3.2. Literature Review
3.2.1. Hydrology Process
Hydrology deals with some aspects of water as resources. Specifically hydrology can be defined as a science that deals with space-time characteristics of
quantity and quality of the water of the earth. The hydrology study is encompassing their process, movement, distribution, circulation, exploration, storage,
development and management Singh, 1992. Other definition of hydrology is a science that explains water distribution in liquid and gas form in earth surface. In
applied hydrology the distribution is focused on quantity Sumawiganda, 1992. Hydrologic cycle is a giant nature machine, always constantly running
distillation and pumping system every time. The Sun, supplying heat energy, together with the force of gravity keeps the water moving from the earth to
atmosphere through evaporation and transpiration, and from the atmosphere to earth by condensation and precipitation. Water also moves in land surfaces as runoff and
stream flow, while there are portion of it infiltrates into ground water stores and flow into the ocean. Rainfall is transformed into water discharge by watershed
system. The volume of discharge depends on several factors; soil, climate, topography, and land use. Land use is one of the dynamic factors brought by human
45 activities. It continuously changes along with the need of settlement, agriculture,
transportation, etc.
3.2.2. Catchment Area and Watershed management
Catchment area is land area including river network and streams that have function to receive, collect and flow the water from rainfall to lake or ocean
naturally. Its boundary is determined by topography and by water body that being influenced by land activities.
Watershed management activities are to using land resources, biophysics and socio-economic optimally to gain maximum productivity in long-term and decrease
negative impact and to provide enough water in quantity, quality and good distribution. It implies that characteristics of good watershed are high production
per area, low erosion and good annual water fluctuation Asdak, 2002. According to the forestry department, watershed management is human effort to control the
relationship between natural resources and human being in watershed area including all activities that aimed to build everlasting and harmonious ecosystem,
and increase benefits of natural resources for human sustainability. There are three principles of watershed management that have been identified, they are; 1 the
natural ecology of watershed system as a dynamically balanced system. 2 The factor that affects runoff; and 3 the misdistribution of water in the hydrosphere in
relation to watershed management practice Black, 1995.
3.2.3. Hydrology Model
A model is simplification of a system. It is impossible to develop a model that presents all processes in a system due to its complexity Hartrisari 2007. A system
is a mechanic in which various components interact in such a way to perform a function Handoko 2005. A model is developed for several goals:
Process comprehension in a system Prediction
Decision support system.
46 A model is developed of at least two variables and one or more relationship
between those variable. A variable is a quantity that may assume a succession of value such as annual precipitation. Model variable may be independent or
dependent Black, 1995. In general description of hydrology model is a simple representation from a complex hydrology system Harto, 1993. A system is a
structure, tools, schematic, or procedure that can form real or un-real, and the system connected in a time reference, input or cause of, power or information with
output effect or reaction in comprehensive system Linsley et al, 1986. The hydrologic modeling system is designed to simulate the precipitation and
run-off process of dendritic watershed system. Hydrological process that represented by parameters can be declared conceptually by mathematical models
after identified from field condition by hydrology system. In recent, many developed mathematical models it can simulate a lot of hydrology phenomena.
Parsimony in parameter is a general orientation in developing a hydrology model, while model structure divided two classes of hydrology model which are conceptual
model and physically base model Pawitan, 2004. Whereas, Singh and Woolhiser 2002 stated that Hydrology model is an assemblage, a mathematical description
of components of hydrology cycle. Singh also classified hydrology model based on; process description, time scale, space scale, technique of solution, land use, and
model use. Hydrology model is capable to study the response of land use change at
hydrologic process. Mathematical understanding of equations and manners to presenting hydrology model behavior is used to give mathematical image relatively
complex for hydrology cycle.
3.2.4. Water Yield
Water yields is the amount or volume of water that is available in a certain spot in a flow in a certain time Singh 1989. Further, water production is an
integrated form of discharge as time function that describe the volumetrically relation between rain and its runoff.
Water volume that flows out of outlet as an output of a watershed in a certain period of time is a base for quantifying the hydrological value in a certain watershed
47 Sheridan 1997. Thus, several hydrology models have been developed to estimate
water yield that is accumulated in watershed outlet; employs varied methods, from simple empirical formula to complex simulation models Ponce Shetty, 1995.
The process of water production in a watershed is started from rain that falls in a certain watershed, as described in following flow pattern in Figure 16.
Figure 16. Hydrology Cycle adapted from Chow 1964
Figure 16 shows that water yield in a watershed is the sum of direct runoff and base flow.
3.3. Methodology
To compare the impact of land use change on water yield, a model that based on land use condition in 2010 is developed. The result of model simulation is then
compared with monitoring data for water discharge in Station Empang discharge gage conducted by Balai Besar Wilayah Sungai BBWS Ciliwung-Cisadane. The
data monitoring is also used to calibrate and validate in order to get the model simulation as close as possible to real condition. After the model is calibrated and
validated, it is then employed to simulate with land use in 2030 for each scenario. Simulation uses rain input data as model did in interval period for February
– July 2010.
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3.3.1. Data Preparation
Data source that is used for this research are primary and secondary data. Primary data is collected by observation of field condition to gain understanding on
physical condition of Upstream Cisadane Watershed. Primary data collected e.g. land use, water discharge and soil characteristic in Upstream Cisadane Watershed.
Data requirement for hydrologic model is shown in Table 12.
Table 12. Data Requirement for Hydrological Model.
No Data Type
Source of Data Spatial Resolution
1 Soil map
Puslitanak Derived from semi-detailed soil map
1: 100.000 2
Stream network USGS
Derived from Digital Elevation Model DEM SRTM
30 m 3
Rainfall data
BMKG Derived from daily rainfall
- 4
Water Discharge Public Work Department -
5 Land use map
Derived from forecasted land use -
3.3.2. Hydrologic Model Development
The HEC-HMS rainfall-runoff hydrologic model was developed using HEC- GeoHMS 5.0, an ArcGIS extension program and preprocessor to HEC-HMS. The
program takes advantage of terrain and geographic data publicly available over the Internet. GIS algorithms incorporated within HEC-GeoHMS were used to delineate
a study area based on the stream gage locations. The stream flow gage data provides pertinent information regarding inputoutput stream discharge volumes through the
study area Olivera, 2001. HEC-GeoHMS was further used to delineate drainage networks and sub-
basin boundaries. The SCS runoff and SCS lag equations were both implemented to estimate runoff volumes and the transformation of these volumes toward the
channel network. Parameters for the runoff and transform model components SCS runoff model, SCS lag equation, respectively were initially based on soil and land-
use conditions, determined through the pre-processing of forecasted land use model. Lumped curve number CN values were derived and assigned to each
delineated sub-basin using HEC-GeoHMS.
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