1SPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001 
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built-in Avenue Language, together with other programming 
languages such as VISUAL BASIC and VISUAL C++. 
GIS Interface 
This component provides a two-way communication between the 
system and its users. A system user may interactively delineate 
an area of concern, identify contamination sources to be 
considered, add additional data, or specify a particular planning 
objective. On the other hand, the system can explain to the user 
about each step in the modeling process, and display results 
from running simulation and optimization models. The system 
also provides its users an evaluation of quality of the data, 
accuracy of the results, and level of the uncertainties. If the users 
are not satisfied with the results from the available inputs, the 
system can recommend what data are needed to improve the 
modeling performance. 
This interface links watershed database, various models, and 
system users together, Thus, the developed system can not only 
access and manipulate a great variety of basinwide data and 
provide a wide range of analytical functions and processes to 
prepare data for modeling, but also provide basin planner with 
direct graphic information. For example, users may easily 
modified the tradeoffs between different objectives based on a 
graphical menu, and then obtain solutions under the new 
scenario. This function is useful for decision-makers to review 
the flexible decision space provided by the modeling outputs and 
make their judgement and/or adjustment for the generated 
alternatives. 
Data display is the final stage in the modeling process, which is 
concerned with the communication of geographic information to 
the user. ArcView is used for displaying the modeling results. 
The software allows users to create their own views of 
geographic data. The users may use basic ArcView statistical 
and spatial query functions to selectively output information. The 
Avenue scripting language, as well as VISUAL BASIC and 
VISUAL C++, are used to create user interfaces (Figure 5). 
GIS-LINKED 
ENVIRONMENTAL MANAGEMENT 
DECISION SUPPORT SYSTEM FOR 
THE LAKE ERHAI WATERSHED 
Version 10a 
Figure 5 Examples of user interface for EDSS 
RESULTS AND DISCUSSION 
According to the local authority, protection of water quality in 
Lake Erhai is of the highest priority. Economic development in 
the study basin should not be based on the cost of lake water 
contamination. This leads to four modeling scenarios 
corresponding to different environmental-economic tradeoffs. 
Among them, scenarios 1 provides a balance between 
environmental and economic objectives. It is suitable for the 
existing system and its potential development in the future, and 
is thus recommended for practical implementation. Table 1 
shows solutions to the six objective functions under this 
scenario. 
Table 1 Solutions to objective functions 
Objective Function 
Lower Bound 
Upper Bound 
Economic benefit, $10,000 
414,378 
583,830 
Forest coverage, km 2 
1,712 
1,875 
Soil loss, ton 
12,311,270 
13,377,654 
Nitrogen discharge, kg 
7,838,750 
10,067,193 
Phosphorous discharge, kg 
1,291,956 
1,657,567 
COD discharge, kg 
251,129,094 
348,814,667 
Scenario 2 is suitable for situations when industrial development 
is emphasized, which may lead to increased economic return as 
well as increased risks of lake water pollution problems. This 
scenario corresponds to a relatively optimistic environmental 
management strategy. However, reliability of achieving water 
quality objectives may become dependent upon how pollution 
problems are controlled. Scenario 3 emphasizes on industrial 
water pollution control with the cost of significantly reduced 
economic return. This corresponds to a conservative strategy. 
Potential adjustments of the generated decision plans by 
decision-makers are possible based on the provided computer 
software packages and interfaces. Thus, based on the modeling 
outputs, the post-modeling analyses, and the acquired 
knowledge of the system’s characteristics, many specific 
environmental management actions can be identified. 
For the planning of human activities, the results show that 
economic activities are necessary for regional development. 
Among them, tourism industry would be promoted due to its low 
pollution potential and high economic efficiency. However, the 
related tourist flow is not only related to human efforts for 
improving scenic spots and service sector, but also a number of 
external factors. This means that there exists an upper limit for 
potential tourist flow. Figure 6 provides tourism development 
plan for the seven sub-areas. 
Agriculture is a traditional activity in the basin area. The majority 
of population in the region are farmers. Agricultural activities