Slide 5 of 7
A land and water resource information system can be defined by a set of equations relating land and water characteristics in which the values of the coefficients of the equations depend on the land type. These coefficients may be single valued numbers or they may be sets of numbers, such as the intercept and slope of an equation relating one variable to another.
(1) The landscape is first classified into a set of discrete areas, such as by using a land use map or an overlay of a land use and soils map.
(2) Then, for each type in this classification a transform coefficient (e.g. C, CN, EMC, etc) is determined, either by analysis of observed water data, or by computer simulation of the functioning of a unit area of soil under particular climate and land management conditions. It typically occurs that observed water data are sparse and have a significant amount of scatter in them, such that it is not possible to differentiate the effects of each land type individually. In such cases, the land types may be grouped into larger categories (e.g. urban, agriculture, rangeland), or they may be represented by an indicator variable, such as the percentage of impervious cover which describes the degree of urbanization of areas of a city.
(3) The relationship between land and water characteristics is completed by filling in the transform coefficient table for all cases required.
(4) In thinking about a system for global application, separate coefficient tables for different world regions would be needed because land and water conditions have great spatial variability.