Relationships between watershed unit landscape pattern and agricultural non-point source pollution.

Using geographic information system to support database and Xiahetao watershed as the case,the study established mathematical models for describing pollution production process and calculated the agricultural non-point source pollution load based on watershed unit.

Through comparing three calculation modes of titrimetric analysis,a calculation method taking the chemical formula and its stoichiomotric number as the elementary entity is reasonable.

After description of current regionalization methods on natural disaster, this paper puts forward a new method which use the bottom--up region combination based on the basic unit theory.

Based on the theory of basic unit in natural disaster system, the paper took the agricultural natural disaster system of Hunan province as an example, and support of GIS,32 524 basic unit were divided in Hunan province.

According to the different stage of SC, the paper divides the reliability into two kinds: inherency and operation, gives out such a concept as basic unit and two kinds of analyzing method for reliability.