32
32
3.5 Model Calibration and Verification
Model calibration is process for fine-tuning of the input parameter data; the performance of the model will be improved. Hydrological models require the
procedure of adjusting values of the model input parameters to match model output with measured field data for the selected period and situation entered to the
model Rientjes, 2007. To assess the model performances in terms of hydrological responses to
land cover changes, the validation processes are needed. The simulation results of this model by using different rain gauges will compare using statistical criteria.
The statistical criteria are Nash-Sutcliffe coefficient and relative volume error. The efficiency of Nash-Sutcliffe coefficient Nash and Sutcliffe, 1970 is
defined as:
= 1 − −
− … … … … … … … … … … … … … … … … .. 10
Where Qot
i
and Qsti are observed and simulated daily discharge at time step t
i
respectively and is mean observed daily discharge and N is the total
number of time steps. The relative volume error of this research is needed to calculate in order to
examine the model performances. Relative volume error of this model will calculate using equation 11.
= −
100 … … … … … … … … … … … … . . 11
Where RV
E
is relative volume error, Qot
i
and Qst
i
are observed and simulated daily discharge at time step t
i
respectively.
3.6 Responses of River System to Land Cover Changes on the Catchment
Area
The changes of land cover gave indirect impact to the hydrological responses on the river system. Generally, the impacts of land cover changes in
long terms are changes of the river characteristics such the changes of river discharge extremely and the increasing of runoff. Assessing the effect of land
33
33
cover changes on the river system were simulated using HEC-HMS hydrological model corresponding to historical land cover, hydrological data, and
meteorological data. To meet the objective of this study, the hydrological responses to land
cover changes were simulated by using three scenarios. The scenarios are: 1. First scenario, the hydrological responses will simulate by using three
different time period of existing land cover condition on 1990, 2001, and 2009.
2. Second scenario is using the land coverland use map from long terms of Provincial Spatial Development Plan RTRW.
3. Third scenario is examining the land cover changes trend to predict of hydrological responses in 2020 and 2030.
Kategori