Groundwater potential mapping using geospatial techniques: a case study of Dhungeta-Ramis sub-basin, Ethiopia

Figures & data

Figure 1. The geographic location of Dhungeta-Ramis sub-basin

Figure 2. Conceptual framework adopted for the generation of groundwater potential map

Figure 3. Lithology map of the study area

Table 1. Characteristic features of lithological groups in the Dhungeta-Ramis sub-basin (source: Alemu, 2010; Gebrekidan, 2005; Kebede, 2013; Teklay, Kroner, Mezger, & Oberhonsl, 1998)

No	Code	Lithology	Geological age	Formation properties
1	Pc2b	Boye group	Precambrian	Represented by varying proportion of schists and gneisses interbedded with marble, quartzite, and amphibolite, all metamorphosed in the mid- to upper amphibolite facies.
2	Pc3k	Soka groups		Represented by metavolcanics and metasediments with numerous lenses or pods of mafic-ultramafic rocks.
3	Pc1	Mafic gneisisses		High-grade metamorphic rock
4	Pc2m	Marbles		High-grade metamorphic rocks that could be potential zone of groundwater in the presence of karst formation.
5	Pzt	Wayu sandstone	Paleozoic – Early Jurassic	It composed of (i) medium to coarse grained and compacted sandstone, (ii) interbedded mudstone, shale, and sandstone, and (iii) grayish yellow, medium grained, compacted, and less porous sandstone from bottom to top.
6	Ja	Adigrat formation		It composed of conglomeratic sandstone, then cross bedded coarser sandstone overlain by beds of laminated medium to fine grained siltstone and mudstone with cyclical deposition. Its upper portion is porous.
7	Jh1	Lower Hamanlei formation:	Middle–Late Jurassic	It is marine sediment formed by the flooding of the sea and consists of mixed carbonate-clastic sediments (limestone and Shale)
8	Jh2	Upper Hamanlei formation		It is marine sediment formed by the flooding of the sea and comprised of pure limestone
9	Ju	Urandab formation		In the study area, this formation is represented by (i) thin to very thinly bedded limestone in the southwestern part of the area in the deep cut valleys of Dhungeta and Shannan Rivers, and (ii) coralliferous limestone, burrowed limestone, brachiopod-gastropod bearing limestone, and ammonite bearing limestone, in northeastern part of the area around the upper course of Ramis Rivers.
10	Ka	Amba Aradon formation	Cretaceous	This formation is subdivided into upper and lower member, where the first one is characterized by medium to coarse grained, cross bedded sandstone at the top and interbedded shale, mudstone and siltstone with fine to medium grained sandstone at the bottom, and the later where dominantly fine to medium grained sandstone with interbeds of shale and mudstone with coal seams.
11	Pna1	Alaji basalts	Tertiary	Characterized by aphyric to locally porphyritic basalt
12	Nag	Arba Gugu basalts	Quaternary	made up mostly of porphyritic pyroxene and/or plagioclase basalts
13	Qa	Alluvial sediments		Composed of unsorted composition; coarse grained sand; medium to fine grained sand with variable content of silt and clay.

Figure 4. Land use land cover map of the study area

Figure 5. Lineament density map of the study area

Table 2. Categorization of factors influencing groundwater movement and occurrence and their associated aerial extent within the study area

Parameter	Rank (%)	Class/unit	Potentiality for groundwater storage	Weight	Area coverage (%)
Lithology	25	Arba Gugu basalts (Nag)	Excellent	25	0.04
		Alaji basalts (Pna1)	Excellent	25	4.37
		Alluvial sediments (Qa)	Excellent	25	5.79
		Amba Aradon formation (Ka)	Very good	20	5.49
		Urandab formation (Ju)	Good	15	5.36
		Upper Hamanlei formation (Jh2)	Good	15	43.61
		Lower Hamanlei formation (Jh1)	Good	15	27.06
		Adigrat formation (Ja)	Poor	10	3.84
		Wayu sandstone (Pzt)	Poor	10	0.11
		Marbles (Pc2m)	Poor	10	0.28
		Mafic gneisisses (Pc1)	Very Poor	5	1.48
		Boye group (Pc2b)	Very Poor	5	2.39
		Soka groups (Pc3k)	Very Poor	5	0.19
Land use and land cover	16.5	Waterbody	Excellent	16.5	0.04
		Agricultural area	Very good	14.5	45.68
		Grassland	Good	12.5	24.23
		Forest/woodland	Medium good	10.5	2.17
		Shrubs cover areas	Medium poor	8.5	27.72
		Bare areas	Poor	6.5	0.08
		Settlement areas	Very poor	4.5	0.08
Lineament	15.5	0.82–1.33 (segment per 1 km^2)	Excellent	15.5	6.67
		0.60–0.82	Very good	12	13.91
		0.43–0.60	Good	8.5	22.69
		0.26–0.43	Poor	5	33.30
		0–0.26	Very Poor	1.5	23.43
Slope (degree)	15	0–5	Excellent	15	40.29
		5–10	Very good	12	20.08
		10–15	Good	9	12.33
		15–20	Poor	6	9.49
		20–35	Very poor	3	15.34
		35–78	Null	0	2.46
Drainage density	10.5	0–0.25 (segment per 1 km^2)	Excellent	10.5	1.73
		0.25–0.5	Very good	8.5	25.07
		0.5–0.75	Good	6.5	61.18
		0.75–1.00	Poor	4.5	11.62
		1.00–1.42	Very poor	2.5	0.4
Annual rainfall (mm)	10	1150–1255	Excellent	10	10.44
		1040-1150	Very good	8.5	19.55
		935–1040	Good	7	62.32
		830–935	Poor	5.5	5.70
		720–830	Very poor	4	1.99
Soil	7.5	Sandy clay loam	Excellent	7.5	0.45
		Loam	Very good	6	57.12
		Clay loam	Good	4	34.34
		Clay	Poor	2	8.09

Figure 6. Slope class map of the study area

Figure 7. Drainage density map of the study area

Figure 8. Rainfall map of the study area

Figure 9. Soil map of the study area

Figure 10. Groundwater potential zone map of the study area

Figure 11. Comparison of groundwater prospective area map generated using weighted overlay analysis of multi-criteria techniques and water point (springs, hand-dug, and deep well)

Alemu, T. (2010). Geological evolution of the northern Ogaden basin: A review. Ethiopian Geosciences and Mineral Engineering Association (EGMEA) Congress, November 8 – 9 2008. Earth Sciences for Society in the context of the UN proclaimed International Year of the Planet Earth 2008.

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Gebrekidan, E. (2005). Water balance and effect of irrigation agriculture on the water quality in meteraha area. MSc thesis, Addis Ababa University pp 105.

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Kebede, S. (2013). Groundwater in Ethiopia. Features, numbers and opportunities. Heidelberg, Germany: Springer Hydrogeology. doi:10.1007/978-3-642-30391-3

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