A method for comprehensively evaluating water quality at various points in a water body has been developed based on the fuzzy reasoning. Vagueness in borders of conventional water quality classes formed for each water quality index is quantified by introducing fuzzy sets associated with the classes and nonlinear membership functions. Mamdani method (or min-max-center of gravity method) is employed in the fuzzy reasoning in order to synthesize concentration data on multiple water quality indices. The evaluation method developed in this study can represent the state of water quality at each points with a real number ranging from 0 to 100. The applicability of the method is demonstrated with the series of monthly observed data from April 1980 to March 2010 at 49 monitoring points in Lake Biwa, Japan. Temporal and spatial variations of the synthesized water quality scores at the monitoring points are presented. The application of the fuzzy comprehensive evaluation method would lead to more rational comparison of synthesized water quality at MPs in the lake and to producing useful information in decision-making on water quality management in the water body.
Egypt is implementing more effective irrigation technology to improve its existing irrigation networks in the Nile Delta. Improvements consist of a demand delivery system using mechanical gate structures and controllers to automatically divert water from one portion of a network to another in the desired amount and sequence. We evaluated the irrigation network system under government management before and after these improvements in the existing irrigation networks in the Nile Delta. The overall results indicate that irrigation networks by traditional rotation systems is unsuitable for irrigation districts located at the end of large irrigation networks in the Nile Delta, while, the demand delivery concept is successful in improving water delivery performance over that of the traditional rotation delivery concept used previously. The new system provided fair shares of water among irrigation districts and allows the irrigation districts to deliver water from main system whenever they need it and any time. In addition, the automation improves efficiency, responsiveness, and flexibility of canal system.
Makabe, which is located in the southern-most part of the main Okinawa Island, is an upland agricultural area that produces sugarcane and vegetables. Geographic features in Makabe-South have created a flood-prone basin that make it one of the most flood-damaged areas in Okinawa. For example, in August 2007 a heavy rainfall event resulted in flood damage over an area of 20 ha. Several measures have been proposed to help mitigate flood damage in this region, which features a relatively complex drainage system. To evaluate and compare these proposed measures, it is important to understand the infiltration mechanisms at work in the area. We use a surface runoff model to compute rainfall outflow for our study site. To simulate the study site's complex infiltration and drainage system, we model two adjacent infiltration ponds with different infiltration capabilities. Among other factors, infiltration rates depend on overflow between these two adjacent ponds, which occurs through both a subterranean and pipe flow drainage system. The simulation results indicate that our modeling approach is useful for evaluating the flood mitigation measures proposed in this region.
The distribution and the habitat characteristics of kitanomedaka in the canals and the ditches around Kahoku-gata, Ishikawa, Japan were investigated in September and October 2001, August 2002, November 2003, during the transient period from irrigation period to non-irrigation period. The investigations revealed the distribution of medaka habitats in the lowland around Kahoku-gata. In the study areas, the habitats were not continuous but rather segmented and isolated. The multiple linear regression analysis indicated that the water surface coverage of vegetation, water surface width and flow velocity were correlated with the medaka population during the non-irrigation period. During the irrigation period, the canal type was correlated with the medaka population although the determination coefficient was very low. In addition, some habitats of medaka in the middle of the Unoke River basin were also reported based on the investigation conducted in December 2004 and January 2005.