Blue-green water resource availability dynamics in the upper Awash basin, central Ethiopia: implications for agricultural water scarcity assessment

Figures & data

Figure 1. Location map of the upper Awash basin and its watersheds.

Table 1. Input data type and sources for blue and green water flow (GWF) estimation using the InVEST model and agricultural water scarcity indices.

Data input	Resolution/Time	Data source/Remark
Observed rainfall and temperature	Daily and annual (2000-2010)	National Meteorological Agency (NMA)
Satellite rainfall	Annual, Raster format (.tif), 0.05º, 2020	WaPOR database https://wapor.apps.fao.org/home/WAPOR_2/1 and https://aquastat.fao.org/climate-information-tool/complete-climate-data
Digital Elevation Model (DEM)	30 m × 30 m	Shuttle Radar Topographic Mission (SRTM) https://earthexplorer.usgs.gov/
Observed stream flow	Monthly and annual (2000-2010)	Ministry of Water and Energy of Ethiopia
Gridded evapotranspiration (ERA-5)	Annual, raster format (.tif), 0.25º (2000-2010 and 2020)	ECMWF's Copernicus Climate Change Service product (https://app.climateengine.com/climateEngine).
Soil depth and root depth	Raster format (.tif)	Adane et al. (2021), Harmonized World Soil Database (HWSD) (https://www.fao.org/soils-portal/data-hub/soil-maps-and-databases)
Plant Available Water Content (PAWC)	Raster format (.tif)	Adane et al. (2021), HWSD document, and Soil-Plant-Air-Water (SPAW) software
Land use land cover (LULC)	Raster format (.tif) (2000, 2010 and 2020)	Hirpa et al. 2023
Biophysical attribute	Microsoft Excel in .csv format	Adane et al. (2021), Allen et al. (1998) and other literature
Basin and watersheds	Shapefiles (.shp)	Delineated using ArcSWAT
Green and blue water footprints for maize, sorghum, and sugarcane	Decadal average (2000-2010)	Hirpa et al. (2022)

Figure 2. Methodological framework for computation of green-blue water resources in the upper Awash basin.

Table 2. Biophysical table of the upper Awash basin.

Description	LUcode	root_depth (mm)	Kc	LULC_veg
ST	3	0	0.300	0
GL	4	500	0.865	1
CL	7	550	0.920	1
BL	6	500	0.150	0
WB	1	0	0.000	0
FL	5	1100	1.000	1
SL	2	600	0.650	1

LUcode: the land use code assigned in land use maps of 2000, 2010 and 2020; Kc: evapotranspiration coefficient based on the FAO guidelines (Allen et al. 1998); LULC_veg: a land use type covered with vegetation assigned 1 (for vegetated LULC) and 0 for all other LULC; root_depth: the depth where 95% of root biomass occurs (Chen et al. 2008); ST: Settlement; GL: Grassland; CL: Cultivated land; BL: Bare land; WB: Waterbody; FL: Forest land; SL: Shrubland.

Figure 3. Spatial distribution of the input data for estimating the green and blue water flows of the upper Awash basin for the year 2000.

Figure 4. Spatial distribution of the input data for estimating the green and blue water flows of the upper Awash basin for the year 2010.

Figure 5. Spatial distribution of the input data for estimating the green and blue water flows of the upper Awash basin for the year 2020.

Table 3. Model validation criteria (Moriasi et al. 2007).

Rating	NSE	PBIAS (%)	RSR
Very good	0.75 ≤ NSE ≤ 1.00	PBIAS < ±10	0.00 ≤ RSR ≤ 0.50
Good	0.65 < NSE ≤ 0.75	±10 ≤ PBIAS < ±15	0.50 < RSR ≤ 0.60
Satisfactory	0.50 < NSE ≤ 0.65	±15 ≤ PBIAS < ±25	0.60 < RSR ≤ 0.70
Unsatisfactory	NSE ≤ 0.50	PBIAS ≥ ±25	RSR > 0.70

Table 4. Water scarcity index ranges (Hoekstra et al. 2012; Xie et al. 2020).

Range	WSIblue type	Range	WSIgreen type
WSIblue < 1	Low water stress	WSIgreen < 0.5	Low water stress
1 ≤ WSIblue < 1.5	Moderate water stress	0.5 ≤ WSIgreen < 1	Moderate water stress
1.5 ≤ WSIblue ≤2	Significant water stress	1 ≤ WSIgreen ≤ 1.5	Significant water stress
WSIblue > 2	Severe water stress	WSIgreen > 1.5	Severe water stress

Figure 6. Validation of the blue water flow at different watersheds in the upper Awash basin.

Table 5. Land use land cover areal coverage and percent share in the upper Awash basin (Hirpa et al. 2023).

LULC classes	Land use area (ha)			Land use share (%)
	2000	2010	2020	2000	2010	2020
WB	22,662	23,943	23200	1.0	1.0	1.0
SL	321,549	335,275	180,799	13.5	14.1	7.6
ST	13,782	33,348	73,271	0.6	1.4	3.1
GL	35,763	6,029	12,551	1.5	0.3	0.5
FL	214,682	152,068	72,919	9.0	6.4	3.1
BL	460,151	277,490	159,266	19.4	11.7	6.7
CL	1,307,523	1,547,958	1,854,106	55.0	65.1	78.0

WB: Water body; SL: Shrubland; ST: Settlement; GL: Grassland; FL Forest land; BL: Bareland; CL: Cultivated land.

Table 6. Decadal hydro-climatic conditions and green and blue water flow in upper Awash basin.

Basin	Year	Area (km^2)	MAR in mm/yr	PET in mm/yr	GWF in mm/yr	BWF in mm/yr	BWF (x10^6) (m^3/yr)
Upper Awash Basin	2000	23761	885.98	1076.74	676.68	208.42	4950.34
	2010		1035.51	1161.73	757.14	277.42	6589.10
	2020		1048.38	1438.50	820.86	226.14	5371.13

MAR: Mean annual rainfall; PET: Potential Evapotranspiration; GWF: Green Water Flow; BWF: Blue Water Flow.

Figure 7. Box plot showing the median, quantile, and range of (a) annual rainfall; (b) annual potential evapotranspiration (PET); (c) annual green water flow (GWF); and (d) blue water flow (BWF) distributions of the upper Awash basin. Aka: Akaki; Hom: Hombole; Kes: Kessem; Kok: Koka; met: Metehara; Moj: Mojo; NHo: Holleta; Sir: Sire.

Table 7. Interannual variability of hydroclimatic variables in the upper Awash basin between 2000 and 2010.

Hydro-climatic Components	Coefficient of variation in watersheds (%)
	Aka	Hom	Kes	Kok	MeK	Met	Moj	Hol	Sir
Rainfall	12.36	17.53	13.91	15.18	14.80	15.92	15.46	19.22	11.84
PET	2.43	3.82	9.77	4.92	3.12	14.02	3.13	3.96	3.11

Aka: Akaki; Hom: Hombole; Kes: Kessem; Kok: Koka; Met: Metehara; Moj: Mojo; Hol: Holleta; Sir: Sire.

Figure 8. Spatial and temporal variation of available water resources in the upper Awash basin: (a to f) the decadal green and blue water flow; (g-i) 12–years average blue and green water flows and green water storage across the basin, respectively.

Table 8. Interannual variability of blue and green water flow in the upper Awash basin between 2000 and 2010.

Freshwater Components	Coefficient of variation in watersheds (%)
	Aka	Hom	Kes	Kok	MeK	Met	Moj	Hol	Sir
GWF	4.76	10.02	10.77	10.37	4.81	13.88	8.98	4.92	4.93
BWF	36.13	50.47	27.90	32.60	29.35	31.81	46.63	22.75	38.66

Aka: Akaki; Hom: Hombole; Kes: Kessem; Kok: Koka; Met: Metehara; Moj: Mojo; Hol: Holleta; Sir: Sire.

Figure 9. The decadal green water flow (GWF) and green water storage (GWS) in different watersheds (a and b) and in different LULC (c and d) of the upper Awash basin. Ho: Holleta watershed; Sir: Sire watershed; MeK: Melka-Kuntire watershed; Hom: Hombole watershed; Moj: Mojo watershed; Aka: Akaki watershed; Kok: Koka watershed; Kes: Kessem watershed; Met: Metehara watershed. FL: Forestland; CL: Cultivated land; GL: Grassland; SL: Shrubland; Set: Settlement; BL: Bare land; WB: Waterbody.

Table 9. Green water flow for different land uses in the upper Awash basin.

Land use class	2000	2010	2020
	GWF (m^3/ha/yr)	GWF (m^3/ha/yr)	GWF (m^3/ha/yr)
WB	24.2	21.9	34.1
SL	7213.4	7585.1	7174.0
ST	4969.0	4681.6	4956.7
GL	7516.5	8196.9	8123.8
FL	8438.4	9638.5	10139.0
BL	3013.1	2947.0	3076.0
CL	7996.0	8826.9	8815.0

WB: Water body; SL: Shrubland; ST: Settlement; GL: Grassland; FL Forest land; BL: Bareland; CL: Cultivated land.

Figure 10. The decadal blue water flows (BWF) in (a) different watersheds of the upper Awash basin; and (b to d) LULC. MeK: Melka Kuntire sub-basin, Aka: Akaki watershed; Ho: Holleta watershed; Kok: Koka watershed; Sir: Sire watershed; Met: Metehara watershed; Kes: Kessem watershed; Hom: Hombole watershed; Moj: Mojo watershed. FL: Forestland; CL: Cultivated land; GL: Grassland; SL: Shrubland; Set: Settlement; BL: Bare land; WB: Waterbody.

Table 10. BWF Proportions in different land uses and years in the upper Awash basin.

Land classes	BWF2000 (m^3/ha)	BWF2000 in m^3 (x10^9)	BWF2010 in (m^3/ha)	BWF2010 in m^3 (x10^9)	BWF2020 in (m3/ha)	BWF2020 in m^3 (x10^9)	Average BWF in m^3 (x10^9)
WB	8302.1	0.19	9463.4	0.23	9158.5	0.21	0.21
SL	1457.6	0.47	2262.7	0.76	1106.5	0.20	0.48
ST	5836.7	0.08	7016.1	0.23	6317.9	0.46	0.26
GL	1897.3	0.07	5286.2	0.03	3885.8	0.05	0.05
FL	535.1	0.11	1109.8	0.17	1083.6	0.08	0.12
BL	5241.3	2.41	5857.7	1.63	5569.2	0.89	1.64
CL	1237.9	1.62	2289.3	3.54	1877.4	3.48	2.88
Total	24507.9	4.95	33285.4	6.59	28998.9	5.37	5.64

BWF: Blue water flow; WB: Waterbody; SL: Shrub land; ST: Settlement; GL: Grassland; FL: Forest land; BL: Bare land; CL: Cultivated land.

Table 11. Green water scarcity index of the rainfed crops in upper Awash basin.

Areas	Rainfed crops	Area (ha)	Av. WFgreen^a x 10^8 (m^3)	WRgreen^b x10^8 (m^3)	WSIgreen^c	WSI level
Debrezeit	Teff	190,818	8.05	15.9	0.51	Moderate
	Maize		7.96		0.5	Moderate
Wonji	Maize	58,544	2.16	5.98	0.36	Low
Melkassa	Maize	94,571	3.63	9.05	0.4	Low
	Sorghum		3.63		0.4	Low

^a AV. WFgreen is the average green water footprint (Hirpa et al. 2022).

^b WR_green is green water resource quantified based on the average green water storage.

^c WSI_green is the green water scarcity index.

Table 12. Blue water scarcity index of the irrigated sugarcane in upper Awash basin.

Areas	Irrigated crops	Area (ha)	Av. WFblue^a x10^8 (m^3)	WRblue^b x 10^8 (m^3)	WSIblue^c	WSI level
Wonji	SC-1^d	12,800	2.34	1.56	1.5	Significant
	SC-2^e		1.36		0.87	Low
Metehara	SC-3^f	10,230	2.15	2.37	1	Moderate
	SC-4^g		1.52		0.64	Low

^aAv. WF_blue is average blue water footprint (Hirpa et al. 2022).

^bWR_blue is the blue water resource from runoff yield.

^cWSI_blue is the blue water scarcity index.

^dSC-1 is sugarcane variety with length of growing periods (LGPs) of 24-month in Wonji.

^eSC-2 is sugarcane variety with LGP of 14-month in Wonji.

^fSC-3 is sugarcane variety with LGPs of 20-month in Metehara; ^gSC-4 is sugarcane variety with LGPs of 14-month in Metehara.

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