ABSTRACT
Fuzzy logic, system, and modeling techniques were presented in previous chapters and now it is time to present some applications concerning various elements of the hydrological cycle. Each element is presented individually and then related to the closest hydrological element as a dependent variable. Almost all deterministic, stochastic equations, algorithms, and models can be fuzzied by considering reasonable fuzzication of the input and output linguistic variables. Additionally, their interrelationships can be put into a set of fuzzy rules as a rule base
The main hydrologic driving force for evaporation is the “temperature” variable, which can be divided into a range of linguistic categories such as “cold,” “cool,” “medium,” “warm,” and “hot” fuzzy classes, as already explained in Chapter 2 (Figure 8.1). Dening the bounds of these states is a bit subjective. An arbitrary crisp threshold might be set to separate “warm” from “hot” but this would result in a discontinuous change when the input value passes over that threshold. The way around this is to make the states fuzzy, that is, allow them to change gradually from one state to the next. For any given temperature value, almost always two successive MFs are triggered with different MDs. For instance, as shown in Figure 8.1, 0.2 “cool” and 0.8 “cold” MDs appear for T12 or 0.3 “warm” and 0.7 “hot” for T45.
