increase soil erosion. The increase in soil erosion will increase the runoff water down stream which might 
in turn contaminate drinking water. Contaminated water will have a negative impact on the public health. 
On the other hand the assessment of the impact of any proposed environmental program should account for 
its impact on all the related levels. For example there could be three levels of decision making in a country. 
An environmental program for protecting watersheds is initiated to cover the whole country, i.e., national 
level, the impact of the program is assessed for each main river basin, i.e., regional level, an 
implementation plan is developed for watersheds, i.e., local level 1 . Ideally, the collective impact of the 
management plans, at the local level, should be aggregated to both the regional and the national levels in 
order to achieve an optimized national environmental program. 
Data 
Objectives 
Analysis 
zoning and aggregation rules 
Basin water 
quality analysis 
Output 
degraded zones 
Output 
Data 
-y— 
New scenario 
U 
OK 
= _N 
Y 
Objectives 
y 
OK - 
* 
N 
Y 
Analysis 
single events 
continuos models 
— ▼ 
Output 
aggregated impact 
of MP’s on watershed 
prioritized areas 
Data 
ZZI 
Objectives 
IZ.ZIZZ. 
Analysis 
MP’s effectiveness 
Output 
Implementation of MP’s 
□ Nauonäl scale 
□ Regional Scale 
□ Local Scale 
Figure 11nterrelation Between The Three Levels of Decision making 
In reality the objectives at the different levels may look contradicting. In fact, this impression is the 
consequence of the attempt to achieve them in isolation. They must be seen as objectives for managing 
only one resource and not several and distinct ones. Thus, the interaction is nothing but the result of the 
functional relationships imposed by the various environmental views of the resource exploitation. This 
functional relationship between levels, Figure 1, can be summarized as follows: 
1 Our concept is not bounded to the local, regional, and national levels of decision making. The intention is to stress 
need for linking levels of decision making whatever these levels are.