Assessing the Implications of Water Harvesting Intensification on Upstream-Downstream Social-Ecological Resilience: A case study in the Lake Tana Basin
Yihun Dilea,b, Raghavan Srinivasanc, Louise Karlbergb, and Johan Rockströma
aStockholm Resilience Center, Stockholm University, Stockholm, Sweden bStockholm Environment Institute, Stockholm, Sweden
cTexas A&M University, Texas, USA
Rationales Rainfall variability – dryspells and droughts
Dry spells Drought
Water harvesting systems can bridge this rainfall variability In-situ water harvesting Ex-situ water hatvesting ? Upstream-downstream implications
Research Area
WH suitability study Hydrological Modelling Understanding implications
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Data Land cover types
Area (% of basin)
Dominantly cultivated 51.35 C2: Moderatly cultivated 22.34
Woodland open; Shrubland; Afro alpine; Forest 2.91 Grassland 2.83 Water body 20.19
FAO soil name Area (% of basin) Texture
Eutric Leptosols 12.38 LOAM Haplic Nitisols 1.29 CLAY_LOAM Chromic Luvisols 16.00 CLAY_LOAM Eutric Vertisols 11.74 CLAY Eutric Cambisols 0.01 LOAM Eutric Fluvisols 9.79 LOAM Haplic Luvisols 20.62 LOAM Eutric Regosols 0.28 SANDY_LOAM Lithic Leptosols 2.86 CLAY_LOAM Haplic Alisols 4.77 CLAY
Basin Area: 15129 km2 Total No subbasins: 959 Subasin sizes: 500-3000ha Total No HRUs: 9963 Flow calibrated at 3 gauging stations
Climate data rainfall, Max & Min - 1990-2011 Global weather data – weather genrator
Evapotranspiration Hargreaves’s method
Surface runoff estimation Curve number method
Stream routing Variable storage method
Hydrological data 1990-2007
Model setup and simulation
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Management Two reserviors Principal spillway Emergency spillway
Elevation* Area(km2) Volume(Mm3) Elevation Area(km2) Volume(Mm3) Lake Tana 1784 2,766 20,300 1787 2983 29,100 Angereb Reservior
2135 0.5 3.53 2138 0.6 5.16
Tillage operations
depth of till of 15cm, and mixing efficiency of 0.3 tillage frequency of 4
Fertilizer application
Pescticide application 2.4.D amine weed killer 1 liter/ha ~ 0.379kg/ha
Model Calibration and Validation at Megech
NSE=0.76 PBIAS=4.0%
NSE=0.74 PBIAS=40.2%
Subbasins No.: 482 HRUs No.: 786 Total area: 10 sq.km Subbasin size: 1-6ha
Climate data rainfall, Max & Min - 1990-2011
Evapotranspiration Hargreaves’s method Global weather data – weather genrator
Surface runoff estimation Curve number method
Stream routing Variable storage method
Model setup and simulations
Management Ponds implemented as reserviors
size that can store water for ONSEASON and OFFSEASON irrigation size determined for combination of different climatic years & nutrient application
Crop rotation is applied ONSEASON (July-Dec) – TEFF OFFSEASON (Jan-April) – Onion
Fertilizer Current fertilizer application for TEFF Blankert fertilizer recommendation (MoAR) for TEFF Blanker fertilizer recommendation for Onion
Pescticide application 2.4.D amine weed killer 1 liter/ha ~ 0.379kg/ha
Tillage operations depth of till of 15cm, and mixing efficiency of 0.3 tillage frequency of 4
Water Harvesting Implementation Scenarios First class suitability – HRUs that consist of a slope<2%, Soil: Luvisols, and Vertisols; and agricultural land. Area = 0.14km2 (1.14% of watershed) Second class suitability – HRUs of slope: <8%; Soil: Luvisols, and vertisols; and agricultural land. Area = 3.79km2 (38% of watershed) Third class suitability – HRUs of slope: <12%; soil: Luvisols, and vertisols; and agricultural land. Area = 5.07km2 (51% of watershed) Nutrient scenarios Current nutrient application rate
TEFF – 1st stage: UREA - 15kg/ha and DAP – 15kg/ha 2nd stage: UREA – 15kg/ha Onion – 1st stage: UREA – 85kg/ha, and DAP – 30kg/ha 2nd stage: UREA – 85kg/ha
Blanket Nutrient Recommendation (BNR1) TEFF – 1stage: UREA – 50kg/ha, and DAP – 30kg/ha 2nd stage: UREA – 50kg/ha Onion – 1st stage: UREA – 85kg/ha, and DAP – 30kg/ha 2nd stage: UREA – 85kg/ha
Blanket Nutrient Recommendation (BNR2) TEFF – 1st stage: UREA – 85kg/ha, and DAP – 30kg/ha 2nd stage: UREA – 85kg/ha Onion – 1st stage: UREA – 85kg/ha, and DAP – 30kg/ha 2nd stage: UREA – 85kg/ha
Change in crop yield (%)
Change in crop yield (%)
Change in biomass (%)
Change in biomass (%)
Onion production (ton/ha)
year IRR VOL(m^3) WYLD(m^3) percentage
1995 (drier) 532,485.68 1,839,334.07 28.95
2000 (wetter) 309,326.90 7,063,383.30 4.38
Discussion and conclusion
U/S Benefits/costs D/S Benefits/costs
Crop yield +++ + Biomass +++ + Soil loss ++ ++ Low flows + ++ Peak flows + ++ Total flow -
Win-Win
Thank you