Integrating WaTEM/SEDEM model and GIS-based FAHP Method for Identifying Ecological Rainwater Harvesting Sites in Ziz upper watershed, SE Morocco

Abstract Moroccan southeast areas have limited water ressources, vulnerable to climate change and characterized by a significant spatio-temporal variability. In response, to ensure the availability of water for local comunity, it is advised to develop some alternatives that improve the local water resources management throughout these areas. Rainwater harvesting (RWH) has been used widely as an alternative technique towards water scaricity. However, taking into account socio-economic constraints for identifying ecological sites for RWH remains a complex task for water managers. The present study was conducted using WaTEM/SEDEM model, GIS techniques and Fuzzy Analytical Hierarchy Process (FAHP) method to identify important ecological RWH sites. For this purpose, several data sources were employed to generate needful thematic layers. The soil conservation service curve number (SCS-CN) method was utilized for preparing a yearly runoff potential map. Then, the thematic layers were weighted for generating RWH suitability map. The results show that yearly surface runoff ranges from 136 to 500 mm. Moreover, the spatial distribution map of soil erosion of WaTEM/SEDEM shows that Ziz upper watershed can be classed into four classes: (i) slight (very suitable), (ii) moderate (suitable), (iii) high (less suitable) and (iv) severe (not suitable). Aproximatly 76.1% of the study area falls within slight soil erosion class. The GIS tools were used for generating the important ecological RWH suitability map. The GIS’s intersect tool was used to eliminate insuitable soil erosion classes and the buffer tool was used for integrating the socio-economic factors including the distance from residential areas and agriculltural fields. Prediction accuracy of the resultant map of RWH suitability showed the value of the area under the curve (AUC) equal to 59.6% for FAHP method in this study. Ecological RWH map, mainly, introduced western areas and some central parts of Ziz upper watershed as suitable RWH areas. The present study demonstrated that coupling WaTEM/SEDEM model with FAHP method and GIS tools provide a valuable approach for identifying the ecological RWH sites in large semi-arid areas.

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Integrating GIS-Based MCDA Techniques and the SCS-CN Method for Identifying Potential Zones for Rainwater Harvesting in a Semi-Arid Area

Water ◽

10.3390/w13050704 ◽

2021 ◽

Vol 13 (5) ◽

pp. 704

Author(s):

Hussein Al-Ghobari ◽

Ahmed Z. Dewidar

Keyword(s):

Water Conservation ◽

Surface Runoff ◽

Rainwater Harvesting ◽

Global Climate ◽

Remote Sensing Data ◽

Curve Number ◽

Drainage Density ◽

Promising Alternative ◽

Thematic Layers ◽

Scs Cn

An increasing scarcity of water, as well as rapid global climate change, requires more effective water conservation alternatives. One promising alternative is rainwater harvesting (RWH). Nevertheless, the evaluation of RWH potential together with the selection of appropriate sites for RWH structures is significantly difficult for the water managers. This study deals with this difficulty by identifying RWH potential areas and sites for RWH structures utilizing geospatial and multi-criteria decision analysis (MCDA) techniques. The conventional data and remote sensing data were employed to set up needed thematic layers using ArcGIS software. The soil conservation service curve number (SCS-CN) method was used to determine surface runoff, centered on which yearly runoff potential map was produced in the ArcGIS environment. Thematic layers such as drainage density, slope, land use/cover, and runoff were allotted appropriate weights to produced RWH potential areas and zones appropriate for RWH structures maps of the study location. Results analysis revealed that the outcomes of the spatial allocation of yearly surface runoff depth ranging from 83 to 295 mm. Moreover, RWH potential areas results showed that the study areas can be categorized into three RWH potential areas: (a) low suitability, (b) medium suitability, and (c) high suitability. Nearly 40% of the watershed zone falls within medium and high suitability RWH potential areas. It is deduced that the integrated MCDA and geospatial techniques provide a valuable and formidable resource for the strategizing of RWH within the study zones.

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A GIS-based approach for identifying suitable sites for rainwater harvesting technologies in Kasungu District, Malawi

Water SA ◽

10.17159/wsa/2021.v47.i3.11863 ◽

2021 ◽

Vol 47 (3 July) ◽

Author(s):

F Nyirenda ◽

A Mhizha ◽

W Gumindoga ◽

A Shumba

Keyword(s):

Moisture Content ◽

Rainwater Harvesting ◽

Curve Number ◽

Physical Factors ◽

Retention Performance ◽

Significant Difference ◽

Suitability Map ◽

Runoff Potential ◽

Level Of Significance ◽

The Impact

A GIS-based approach for identifying suitable sites for rainwater harvesting (RWH) technologies was developed and applied in Kasungu District, Malawi. Data were obtained from reports, socio-economic survey documents of the area and maps. Field surveys were conducted in the villages of Chipala Extension Planning Area (EPA), in order to identify and evaluate the performance of existing RWH interventions, and determine factors for locating suitable areas for RWH. Observed soil moisture content was used to assess the water retention performance of the prevalent RWH technologies: contour tied ridging and soil mulching. A GIS-based Soil Conservation Service Curve Number (SCS-CN) method was used to map runoff potential for areas with RWH technologies, using physical factors of rainfall, land use, soil type and slope to estimate runoff potential. This was then integrated in a GIS database, with social-economic factors in the form of household income level and environmental factors, including impacts of implementing RWH, to determine the suitability of land areas for RWH in Kasungu District. One way analysis of variance (ANOVA) was used to test the impact of identified technologies by comparing the moisture content measurements for each of the identified technologies at 5% level of significance. The ANOVA results showed a statistically significant difference in the moisture measurements for the three technologies identified (P < 0.05). The RWH suitability map for the study area showed that 0.2% of the area considered had very high potential, 33.5% high, 55.9% moderate, 10.1% marginal and 0.3% not suitable for in-field RWH. The model was verified by locating the existing RWH on the suitability map obtained from GIS: 81% of RWH were located in the highly and moderately suitable areas whilst only 13% were located in areas of low suitability. Hence the developed model can reliably be used to predict potential areas for RWH.

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