Paper Information

Journal:   IRAN-WATER RESOURCES RESEARCH   SPRING 2017 , Volume 13 , Number 1 #M0054; Page(s) 126 To 138.
 
Paper: 

ANALYZING THE EFFECT OF UNCERTAINTY OF SOIL PARAMETERS ON SOIL MOISTURE PROFILE UNCERTAINTY USING FUZZY SET THEORY

 
Author(s):  KHORAMI M., GHAHRAMAN B.*
 
* DEPARTMENT OF WATER ENGINEERING, FERDOWSI UNIVERSITY OF MASHHAD, MASHHAD, IRAN
 
Abstract: 

Uncertainty is the measure of reliability associated with a particular set of results. There are lots of parameters affecting the water movement through the unsaturated zone measurement or estimation of which are a difficult task encompassing uncertainties of some kind. In this study, a methodology based on fuzzy set theory is presented to express imprecision of input data, in terms of fuzzy number, to quantify the uncertainty in predictions. Richards’ equation as a certain model was solved numerically. To estimate the uncertainty in the model the input parameters (qs, qr, Ks, a, and n) were introduced as fuzzy parameters. After introducing suitable fuzzy membership functions for input parameters, boundary values were obtained for each parameter for different b-cut levels in input parameters. Using these values and considering different result interval boundaries, the mathematical operation on fuzzy sets are performed resulting in the moisture values in specific times and locations. Corresponding to different b-cuts, fuzzy membership functions were derived for soil moisture at any time and depth. The results showed that uncertainty in simulating soil moisture profile was minimum in saturated phase and maximum in advance phase. This was because of the maximum number of parameters taking part in maximum uncertainty in the later phase. The shape of fuzzy membership function for soil moisture in specific time was varying for different depths corresponding to the different role of the effective initial parameters in any time and depth.

 
Keyword(s): UNSATURATED ZONE, NUMERICAL SOLUTION, RICHARD’S EQUATION, HYDRUS
 
References: 
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