Call for Papers
Application of System Dynamics on Watershed Management
in Java Island, Indonesia
By
Prasetyo Sunaryo, Tusy A. Adibroto, Hary Budiarto, and Ervan Maksum
Researcher for the Agency for the Assessment and Application
of Technology (BPP Teknologi)
ABSTRACT
The sustainability of a Watershed (DAS) ecology depends on numerous factors, especially
land and water availability. Transformations occurring on a DAS be seen from the forest openings in
the upstream to the conversions of rice fields into settlements and industrial area in the downstream.
* These transformations determine the water sycle of a DAS, such as soil absorbency, thereby affecting
the eiver’s waterflow and quality. Mismanagement on the upstream area, in addition, may affect the
downstream area.
This paper is aimed to observe and understand the occurring transformations on DAS in Java
Island - Indonesia., thus provide the basic considerations for well-managed DAS in order to minimize
any possible negative impacts. System Dynamics program is applied to support the analysis.
I. INTRODUCTION
Watershed (DAS) is actually the land stretching along a river. DAS in this paper is
devided in to three parts :
a) Upstream DAS; covering forests, farmland/ricefields, and settlements
b) Downstream DAS; covering settlements, farmland/ricefields and industrial area
c) Middle DAS; the transitional area between the two.
Therefore, a DAS area streches from mountainous to coastal area regardless any
administrational borders. The DAS model applied here is conducted through a dynamic model
analysis of which data is taken from Indonesian Statistic Bureau (BPS) and from the Study of
Sustainable Development.
Due to its physical and enviromental complexity as well as its significant role for the on
living creatures, DAS is obviously one of the strategic natural resources. Its function is
determined by various biphysical components such as land utilization, soil and other physical
characteristics on its surface. These components, thus, should be maintained and well-balanced
to establish a good supporting DAS. A DAS sustainability in this paper depends on two factors,
Le. the transformation of a) Land utilization and b) water utilization (considering its function as
a water provider). On the other hand, DAS as a waste container is not considered here, since
waste is another specific and complicated problem of its own.
This paper, indeed, focuses on the natural and enviromental problems in Indonesia as
the impacts of four economic tendencies :
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3.
4.
Rapid population growth
Sharp economic growth within the last two decades, mainly caused by oil productions and
exports of other natural resources. ~
Tremendous expansion of food production, indicated by the quick industrialization and
economic growth in Java island
Extensive land exploitation, which often endanger both uphill and downhill environment
System Dynamic is applied to understand the transformations on a DAS and in turn may
serve as the foundation in carrying out suitable plans for a sustainable development.
IL ANALYSIS
2.1. The Purpose of Study
2.2
2.3.
1. To have feedback loop on the land water management in Java Island, hence adds to the
understanding of the causal relationship in the real system (observed).
2. To find a certain ecological limit of the rapid population growth.
3. To figure out the model’s sensitivity, by transforming certain parameters which identify
land and water utilization conducted by people and government.
4. This model is expected to be the foundation in forming DAS management, related with
utilization for industry, farming, and settlements, as the impact of rapid economic
growth.
5. To find solutions to the shortage of land in Java.
. Stucture of The Model
Description of System Dynamic on Land and Water Management in Java Island, Indonesia
The global model of land utilization in Java reveals that more than 36 DAS in Indonesia,
covering 10.4 million Ha, is classified as critical land. This critical land is increasing about
1-2% per year, and about 1/3 (one - third) of it is rice fields in the downstream rice
field/farmland.
Forest is the first area to deal in land utilization. Recently, many forests have been
converted into rice fields, settlements, industrial area or farmland. Needless to say, more
and more rice fields are needed to meet the increasing demand of rice, as the impact of
economic and population growth in Java island. Furthermore, urbanization also accelerates
housing demands, which consequently requires more conversions of fertile rice fields and
farmland into settlements. Today, the government is building up apartments in big cities as
an alternative solution. Yet still is questionable if such effor will solve the land utilization
problems and thus improve the watershed management in Java. Industrial and farmland
expansion are facing the same situation, since the basic problem behind it is the speedy
economic and population growth.
Analysis
As stated above, economic growth is the most significant factor causing land
conversion. Economic growth always results in the increase of primary, secondary and
tertiary needs. In the farmland sub system, the needs for living (vegetables, fruit, meat) is
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2.4.
2.5.
determined by the population growth. Forest conversion into farmland will influence soil’s
infiltration and percolation as the soil becomes condensed and humid.
In the rice field sub system, forests are converted into rice fields to meet the basic need
(rice). In this model, agricultural intensification is assumed to be hampering the forest
growth for rice fields. In rice fields, water supply comes from irrigation.
In the settlement subsystem, the available land comes from forests, farmland and rice
fields. Settlement has become crucial in corelation with economic growth now, since it is
not only a basic need but it has become an economic commodity.
Big investments in settlement development may spoil the land’s functional structures
and ecological activities. Therefore, area limitations are necessary to minimize land
hardening that can avoid water infiltration. In that case, most of rainwater will only be run
- off with significant effects on the ground water supply and the river’s waterflow
fluctuation.
In industrial subsystem, land utilization occurs on the downstream area. Usually, this
area is originated from rice fields or farmland. It is often congested with various economic
facilities, such as factories and offices, which are often closed buildings. The soil, then, can
not absorb the rainwater. Despite its land expansion for industry, economic growth may
result in land inflation, which in tum will suppress the land expansion itself and lead to a
balanced condition.
In hydrological dynamic cycle, land transformations on a DAS bring some changes to
tiver’s waterflow, as the result of run - off and sedimentation. Water volume basically
remains constant, but men’s activities may change the natural cycle process from the
precipitation to evapotranspiration and evaporation. This will differ the water volume in
each catchment area.
Limits and Behavior of the System.
The variables included consists of exogenous, endogenous and omitted ones.
Endogenous variables comprise forests, farmland, industrial area and settlements in the
beginning of simulation. Omitted variables are aimed to limit the problem analysis.
Exogenous variables, expected to change the systems behavior, comprise the population
growth, land prices, housing capacity, living standards, rice production (agricultural
intensification) and water utilization percentage. In addition, a referencial scenario is
consulted (until the year of 2070), covering the following assumptions : a) forest width
converted into consumptive area (settlement, industrial, rice field) at 21%, b) increase of
rice field area at 1,8% year, c) Population at 2% year (regardless the death toll), d)
economic growth at 7% year, e) water supply in Java at 122,700 million m3/year, f)
percentage of water sonsuption for drink at 7,3%, animal farm 0,3% and irrigation 82,4%.
Policy Choises
The ananlysis allows us to ecognize the land and water utilization on DAS im the future,
with respect to the population, land utilization pattern and water consumption. The target
of the policies is to organize land and water functional aspects, thus formulated as follows :
Policy on land utilization , b) Policy on Agricultural technology, c) Policy on the water
resource management and , d) Policy on the population.
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I. CONCLUSION
: number of points can be concluded from the analysis with System Dynamics :
2
Population grwth is a significant variable which influences land and water utilization.
Water availability is determined more by water production in the conversion area than by
people’s consumption. Therefore, water resource conservation can be carried out through
land management in the upstream area.
Forest converting disturbs the hydrological system on the DAS system.
The increase of settlements is not much influential to the land and water functional aspects
(in long term).
Agricultural intensification is necessary to reduce water consumption for irrigation.
Price is an external variable in decision making, since it is affected by supply - demand
tendencies.
A converted forest has certain functional limit, therefore in a long term basis forest
conversion speed will come to a balanced condition.
Industrial and settlement land utilization should proportionally organized, since it is a big
ground water consuming area and yet it is not self - sufficient area in the water supplying.
IV. BIBLIOGRAPHY
Asdak, C., 1995, Hidrologi dan Pengelolaan Daerah Aliran Sungai (Hydrology and
Watershed Management), UGM Press, Yogyakarta, Indonesia
Meadows D. L. and Meadows, D., 1973, Toward Global Equilibrium, Wright Allen Press,
Cambridge, Massachussets, USA
State Ministry of Population and Environment, Kualitas Lingkungan Indonesia, 1995
(Indonesian Environment Quality, 1995), Jakarta, Indonesia
Statistic Bureau Centre, Statistik _Lingkungan Hidup Indonesia, 1993 (Statistic of
Indonesian Environment, 1993), Jakarta, Indonesia
Richardson G. P. and Alexander L. III, 1983, Introduction to System Dynamics Modelling
With Dynamo, MIT Press, Cambridge, Massachussets, USA
Sosrodarsono, S., Takeda, K., 1993, Hidrologi untuk Pengairan (Hydrology for
Irrigation), Pradnya Paramita, Jakarta, Indonesia
Suparmoko, 1994, Ekonomi Sumber Daya Alam dan Lingkungan (Economic Resources
and Environment), BPFE, Yogyakarta, Indonesia
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