Identi cation of Ground Water Potential Zones Using GIS and Remote Sensing Techniques in the Case of Odiyo Watershed, Ethiopia


 Background: The current study conducted to analysis the bottom water potential zones in Odiyo watershed. The study relies on the secondary data, which is collected from concern department and through internet. Totally nine parameters are consider for the study like drainage density, elevation, geology, geomorphology, land use and land cover, lineaments, rainfall pattern, slope gradient and soil texture. The chosen parameters are prepared and classified in GIS environment, then weightage for every parameter and its classes are assigned using Analytical Hierarchical Process, and eventually, weighted overlay analysis in ArcGIS accustomed discover the result. Results: The result relived that, about 183.87ha (0.613%) areas are having very high, 4846.23ha (16.18%) area are having high, 19229.4 ha (64.19%) having moderate, 5645.7ha (18.855) having low and 48.6ha (0.16%) area are having very low potential of well water. Conclusions: The knowledge on strength of ground water supported ground water zones help in management and development of the groundwater within the study area.


Background
Ground water resources are a crucial resource for its use in domestic, agriculture and industries purposes. There has been an incredible increase within the demand for groundwater thanks to increase in population, advanced irrigation practices, and industrial usages (Jha et al., 2007). Hence, unscienti c exploitation and improper use of water policy are possible factors.
Therefore, the assessment of groundwater resources is critical for sustainable management. Most groundwater potential investigation techniques (i.e., geophysical methods, ground based survey, and exploratory drilling) are uneconomical and time consuming and large data sets (Nampak, pradhan, and Manap, 2014; Singh and prakash). However, an integrated GIS and remote sensing study can provide the suitable platform for the convergent analysis of enormous volumes of information and quite higher cognitive process techniques for groundwater exploration.
Recently, several studies are applied using weighted overlay analysis for assessing groundwater potential zones (Tolche, 2020; Groundwater potential zone mapping in Odiyo watershed will have a big effect within the sub basin furthermore because the country. Since the watershed is that the major part to contribute to Omo River; mapping the underground water will enhance sustainable management of groundwater resources within the country. As a result, the current study interested to delineate the groundwater potential zones by using remote sensing and GIS technologies within the study area. Nine determinant factors, namely, lithology, slope, LULC, rainfall, lineaments, geomorphology, elevation, soil texture and drainage density, were accounted for within the study.

Study Area
The study area Odiyo watershed is found within the center portion of Omo basin, Ethiopia. Geographically, the study site is situated between latitude 7°7 0" to 7°25 0" n and longitude 36°23 0" to 36°40 30" e with an aerial extent of 315.52 km 2 (Fig. 1) .the elevation of the area ranges from 3219 to 1190m above average sea level. In step with the national meteorology report, the mean annual rainfall of the area is varies from 1536.7 to 1644.9mm and the mean annual temperature ranges from 12.4 o c to21.5 o c.

Methodology
In order to identify the ground water potential zone within the study area various kinds of data and software are used (Table 1).All criteria employed during this study were rst geo-referenced and converted into a raster format to make ready for reclassi cation and standardization. Following, all the factors were reclassi ed using ArcGIS spatial analysis tool supported their groundwater availability rank. Their levels of groundwater availability were decided supported data collected from the varied scienti c literature. Thus, all the factors were classi ed into ve classes (very high, high, moderate, low and very low) with values ranging from 1 to 5, where 1 represents very low and 5 represents very high. For each criterion, Weights were derived in IDRISI software using AHP methods. All the standardized criteria were combined using weighted overlay analysis to produced ground water Potential Zones Map of the study area. The sources of the quality data used for the delineation of groundwater Potential Zones Map and availability levels were supported published scienti c literature as indicated in Table 2. The overall framework of the research study analysis is presented in Fig. 2.   Tolche, 2020). The drainage density of the study area was prepared from the digital elevation model (30 m х 30 m resolution) in ArcGIS 10.5 platform. The drainage density has been classi ed into ve classes ( The possibility of ground water is high if the rainfall is high and it is low if rainfall is low (Mahalingam and Vinay, 2015). This study has been considering the annual mean rainfall from the year 1980 to 2016. the worth of annual mean values are plated on the respective rain gage stations and also the interpolation method Krigging has been wont to learn the distribution of rainfall within the study area. Once the spatial distribution of rainfall has been found the study area has been classi ed into ve zones supported the equal interval (Table 6 and

Elevation
Water tends to store at lower topography instead of the upper topography. Higher the elevation lesser the ground water potential and the other way around as Gedebo,(2005) citied in Mahalingam and Vinay,(2015). For this study elevation data having 30meter spatial resolution has been created supported the ASTER DEM. The study area's elevation ranges between 1189meters to 3163 meters from the mean water level, this value are classi ed equally into ve classes ( Slope determines the speed of in ltration and runoff of surface water, the at surface areas can hold and drain the water within the bottom, which might increase the ground water recharge whereas the steep slopes increase the runoff and reduce the in ltration of surface water into ground (Mahalingam and Vinay, 2015). The slope of the study area has been calculated in percent supported the DEM model which was supported the ASTER data. The slope has been classi ed into ve classes (Table 8 and Fig. 7) The rate of in ltration largely depends on the grain size and related hydraulic characteristics of the soils (Fashae et al., 2014). Soil texture of the study area is studied from the soil data collected from agricultural department. The study reveals three soil texture class in odiyo watershed namely clay and clay loam. Rank of soil has been assigned on the premise of their in ltration rate (Tripathi et al, 2017). Clay and clay loam soil have low in ltration rate (Table 9 and Fig. 8)  (Table 10 and Fig. 9).

Geology
Groundwater occurrence and its movement depend on the geological setting. Major geological classi cation of the watershed is ingenious rocks. Geological features of the study area are later classi ed in terms of groundwater potentiality (Table 12 and Fig. 11) based on pervious literature (Mwega, 2013).

Weight assignment to parameters
The results of the study indicate that the consistency ratio is 0.03. this is less than 0.1 which is acceptable to continue and apply the AHP method analysis (Saaty,1980).Based on the IDIRISI_AHP weight derivation module, the following eigenvector weights for all criteria considered for groundwater potential zone selection were generated (Table 14).In summary, the results of the AHP weight derivation reveals that parenthetically, soil texture plays an important role with the best score weight of 31

Delineation of groundwater potential zones
After the weightage of each parameter has been determined. Finally, 'Spatial overlay method in Arc GIS environment is employed to conduct overly analysis to get the intended result. The results of overlay analysis has been classi ed into ve classes as very low, low, moderate, high and very high (Fig. 12). From the results of classi cation it is been found that, about 183.87ha (0.613%) areas are having very high, 4846.23ha (16.18%) area are having high, 19229.4 ha (64.19%) having moderate, 5645.7ha (18.855) having low and 48.6ha (0.16%) area are having very low potential of ground water (Table 15). Very high and high groundwater potential zones are concentrated within the area where, high lineament density was illustrated united of the basic factors for groundwater potential zonation (Ibrahim-Bathis & Ahmed, 2016).The low to very low potential zones are mainly distributed within the areas having high drainage density. Hence, the groundwater potential in these areas may be not su cient for irrigation and other livelihood requirements. Therefore, groundwater development activities preferred to be performed in high groundwater prospective zones.

Conclusion
The study on groundwater potential through integration and weightage overlay analysis in GIS environment using physical parameters that in uence the groundwater is being successfully applied during this study. The methodology begins with the preparation of thematic layers from different data sources and next deriving the weights using overlay analysis to search out groundwater potential. The weightage is assigned to different layers and overlaid to realize the intended result groundwater potential zones of odiyo watershed. The thematic layers are rst assigned the weightage supported the precise importance of the category in individual parameters. The layers are then overlaid and therefore the result's then classi ed into ve class supported groundwater availability to namely; very high, high, and moderate, low and very low. The knowledge obtained on the groundwater prospectus of the study area will be accustomed identify and extract the potable water for the domestic and irrigational purposes.

Declarations
Ethics approval and consent to participate Informed consent was obtained from all student participants involved in the study. All participants freely agreed to participate in the study without reservation.

Funding
The authors are not received any fund.

Consent for publication
Consent to publish individual data in any form was obtained from the participants interviewed.

Availability of data and materials
Not applicable' for that section

Competing interest
The authors declare no competing interests.

Authors' contributions
Habtamu D and Dereje B conceived and designed the work validated the method section. Both authors participated in the analysis, validation and writing of the paper. Both authors read and approved the nal manuscript. Locational map of odiyo watershed Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors. Reclassi ed Drainage density map. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.

Figure 4
Reclassi ed Lineament density map. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors. Reclassi ed Rainfall map. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.

Figure 6
Reclassi ed Elevation map. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.

Figure 7
Reclassi ed Slope map. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.

Figure 8
Reclassi ed Soil texture map. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.

Figure 9
Reclassi ed LULC map. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.

Figure 10
Reclassi ed Geomorphology map. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.

Figure 11
Reclassi ed Geology map. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.