1SPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001
applied to the planning of water pollution control in the Lake
Erhai Basin, China. This project was supported by the United
Nations Environment Programme (UNEP) (Huang et al., 1996)
OVERVIEW OF THE STUDY AREA
The study area, Lake Erhai Basin, which covers an area of about
2,565 km 2 , is located in the southwest of China (Figure 1). The
lake is known as a “bright pearl” with unique sightseeing
resources. It is a freshwater lake with a surface area of 250-257
km 2 , an average depth of 10.2 m. There are 117 rivers flowing
into the lake, and only Xier River out of the lake. The lake plays a
crucial role in local economic development, with its resources
available for water supply, agricultural irrigation, fishery, tourism,
and navigation. Economic activities in the basin includes
agricultural and industrial production, net-cage fish culture,
forestry, tourism, and lime/brick production. Currently, the major
environmental problems in the lake basin are: (i) deterioration of
lake water quality and increased soil erosion due to decline of
lake water level; (ii) nonpoint source pollution from crop farming,
livestock husbandry, and fish culture; (iii) water contamination in
Xier River due to industrial wastewater discharge; and (iv)
deforestation in the lake basin coupled with increased soil
erosion, leading to accelerated sedimentation process in the
lake.
SYSTEM DESCRIPTION
Interactive Relationships
Based on the consideration of many socio-economic,
environmental concerns and the requirement of system
modeling, system activities in watershed were divided into
several components, including agriculture, industry, in-lake net-
cage fish culture, tourism, forest, stone excavation, in-lake
navigation, in-lake fishing, lime/brick production, and water
supply. They are related to each other and have direct or indirect
impacts on the system’s environmental and economic objectives.
For example, agricultural production needs water for irrigation,
and generates nonpoint source pollutants due to
manure/fertilizer applications. Water pollution results from
nonpoint source losses of sediment, nitrogen and phosphorus
from farm lands due to land erosion and washing away of
unused nutrients from fertilizers and manure; and irrigation water
allocation is related to farming activities, pipe flows, and
economic returns. High nitrogen and phosphorus concentrations
can lead to eutrophication of water. This should be controlled
under allowable levels corresponding to the objective of lake
water quality (Haith, 1984).
Figure 2 shows interactive relationships among various system
activities and pollution concerns. It is indicated that most of the
activities are not only related to each other but also responsible
to a number of pollution problems. Any change in one activity
may lead to a series of consequences to the others, as well as
the related environmental problems. The problems are also
interrelated to each other. For example, point/nonpoint source
pollution may affect biodiversity, and solid/hazardous waste
generation may contribute to point/nonpoint source pollution.
Between the activities and the problems, there exist potential
abatement measures such as pollution control projects, and
environmental management initiatives. For decisions related to
these actions, careful systems analysis would be needed.
Figure 2 Interactive relationships between human activities and resulting
pollution problems
Dynamic Feature
For the planning horizon, social, economic, legislative, and
resources conditions will vary with time. Reflection of these
temporal variations would be important for generating effective
and realistic planning alternatives. Thus, employment of dynamic
optimization and systems dynamics methods for the study
problem is desired. Due to possibility of continuous changes in
system components along with time, it was suggested this study
should lead to a "real-time" decision support system. This means
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