Evaluating the effect of intensification on water quality: shallow groundwater, streams, lake water bodies & biomass in the Amhara region of Ethiopia

Tilahun, Seifu A.

English

Texas A&amp;M Repository

Irrigation and agriculture development in Africa: Impact on water quality and ecosystem health in the Ethiopian highlandsSeifu A Tilahun et al., 2019Bahir Dar Institute of TechnologyBahir Dar University15 July 2019Study aim• Purpose: Evaluate the effect of intensification on water quality: shallow groundwater, streams, lake water bodies & biomass• Location: Amhara region, EthiopiaDifferent intensification levels & topographyRobit (intensified)~1000 haDangishta (less intensified)~5700 ha• Agricultural land use: 80% (Robit) and 60% (Dangila)• Slope class: 0-43% (Robit) and 0-28% (Dangila)• Irrigation in Robit > Dangila• endosulfan (α+β) 256ml/ha90Kg/ha DAP & 46Kg/ha UREA 72 Kg/ha DAP & 43Kg/ha Urea 90 Kg/ha DAP & 46 Kg/ha Urea0.4 m3 Organic fertilizerWatershed land use pH OM(%) TN(%) Avl.P(mg/l)Robit Bata Farm land 6.0±.18 1.9±.8 0.09±.04 7.7±1.9Grazing land 5.7±.18 3.8±.82 0.188±.04 4.7±1ForestKhat irrig.5.6±.365.8±.133.5±1.83.2±10.17±.090.16±.055.4±1.79.2±4.4Dangishta Farm land 5.1±.18 3.2±.6 0.16±.03 15.8±4Grazing land 4.8±.15 4.5±.5 0.23±.02 9.5±2Forest 5.1±.05 3.6±.5 0.18±.02 11.6±1.7Mean values ±SD of soil chemical parameters from  different land usesSoil characteristics• Soil pH values were higher in Robit Bata than Dangishta • Soil OM , TN and available P (Robit < Dangila)Typical landscapeGroundwater Level Variation OvertimeGroundwater table variations vary across the two watersheds due torainfall distribution and irrigation levelDangishta Year1/2014  5/2014  9/2014  1/2015  5/2015  9/2015  1/2016  5/2016  9/2016  1/2017  5/2017  9/2017  1/2018  5/2018  9/2018  1/2019  Groundwater depth(m)02468101214161820 0102030405060708090100110120130140150UpslopeMid-slopeValley bottomRainfallRobit BataYear1/2014  5/2014  9/2014  1/2015  5/2015  9/2015  1/2016  5/2016  9/2016  1/2017  5/2017  9/2017  1/2018  5/2018  9/2018  1/2019  02468101214161820Daily Rainfall(mm)0102030405060708090100110120130140150UpslopeMid-slopeValley bottomRainfallGroundwater Nitrate• Higher level NO3- was observed during rainy season• Irrigation months (Oct-Dec) higher NO3- compared to dry non-cropping period (Jan-May)• NO3- signficantly lower in valley bottom and lowest in Dangila (P<0.001) • Rainy season: risk of levels above EPA drinking guidelines (10 mg l-1)Groundwater Phosphorus• Rainfed cropping season PO43- was significantly high in both watersheds ( P=.018)• Higher concentration levels in Robit likely related to relase of PO43-from soil in the landscape because of  low soil OM (Robit < Dangila in OM)P-PO43-  (mg.L-1 )0.000.050.100.150.200.250.300.35Mid-slope Mid slopeP-PO43- (mg.L-1 )0.000.050.100.150.200.250.300.35Upslope UpslopeDec/16  Jan/17  Feb/17  Mar/17  Apr/17  May/17  Jun/17  Jul/17  Aug/17  Sep/17  Oct/17  Nov/17  Dec/17  Jan/18  Feb/18  Mar/18  Apr/18  May/18  Jun/18  Jul/18  Aug/18  Sep/18  Oct/18  Nov/18  Dec/18  Jan/19  P-PO43- (mg.L-1 )0.000.050.100.150.200.250.300.35Valley bottomDec/16  Jan/17  Feb/17  Mar/17  Apr/17  May/17  Jun/17  Jul/17  Aug/17  Sep/17  Oct/17  Nov/17  Dec/17  Jan/18  Feb/18  Mar/18  Apr/18  May/18  Jun/18  Jul/18  Aug/18  Sep/18  Oct/18  Nov/18  Dec/18  Jan/19  Valley bottomProcesses control contaminants in GW• MLR analysis produced statistically significant models( P<05)• Cloride and ΔH positively contribute to PO43- in both watersheds • Chloride, potassium, and fluctuation in groundwater table (ΔH) positive contribute to N-NO3- due to dissimilation and dinitrificationN-NO3-=.5+ (.2Cl-) + (-.317Cl-/N-NO3-) + (.156K+) + (.232ΔH)P-PO43- = .027+ (-.006Cl-) + (.008ΔH)ΔH=monthly groundwater table level fluctuation (m)02468100246810N-NO3-Streams: Nitrate and Ammonium  Both nitrate and ammonia were dominant in stream during rainy period Only nitrate was high during dry period.0246810Nov-16Dec-16Jan-17Feb-17Mar-17Apr-17May-17Jun-17Jul-17Aug-17Sep-17Oct-17Nov-17N-NH 4+012345678910Nov-16Dec-16Jan-17Feb-17Mar-17Apr-17May-17Jun-17Jul-17Aug-17Sep-17Oct-17Nov-17Dec-17Jan-18Robit  BataDangishta00.20.40.60.8Nov-16Jan-17Feb-17Apr-17May-17Jul-17Sep-17P-PO43-00.20.40.60.8Nov-16Dec-16Feb-17Apr-17May-17Jul-17Sep-17Oct-17Streams : PhosphorusDangila Dissolved P was high during rainy period in high-flow in the order of 0.6 mgP-PO43-.L-1Robit  BataTotal Nitrogen: spatial12August December March• Concentration of TN is generally lower than WHO permissible limit• Decrease in load and increase in biological activity drive lower TN concentration.Ateka et al. (draft)Total Phosphorus: spatial13August December March• Largest freshwater body (Lake Tana) started to exceed the 0.2 mg/L of P -minimum level for eutrophication • Increasing trend in TP from Aug 2016 to Mar 2017 could be with high internal loadingAteka et al. (draft)Pesticides in groundwater• Endosulfa-α concentrations  were high in rainy period (August) and irrigation (October) period. The  values exceeded MAL- value of EU 0.1 µg L-1• Endosulfa-β in groundwater was not detected during study periodEndosulfa-βMay-16Aug.-16Oct.-16Mar.-170.000.050.100.150.20Sampling periodCon.(µg.L-1 )Pesticides in Stream• Endosulfa-α concentrations  were high during rainy period (August) and irrigation (October) period. The  values exceeded MAL- value of EU 0.1 µg L-1• Endosulfa-β and 2,4-D in streamflow were not exceeded EU MAL in study periodResidue levels in onion and khat biomassB) isomerRaw-onionBoiled-onionKhat02468101214A) isomerRaw-onionBoiled-onionKhatResidue ( g.kg-1)02468101214The EU pesticides regulation for α-and β-endosulfanresidue in bulbs and vegetables recommended a tolerance level of 100 µg.kg-1Key messages for sustainable development• ILSSI project provided evidence for critical institutional changes, guidelines and monitoring mechanisms to regulate agrochemical use and occurance in water bodies• Increase smallholder awarness on the impact of agrochemicals on water quality and human health needed• Target and promote intensified SSI in suitable areas through evidence-base on agriculture-water-environment-health system• Reverse degradation and rehabilitate watersheds (river basins) for improved SSI• Link watershed management with irrigationThank youThis research was supported through Feed the Future Innovation Labs. We are grateful  to Sustainably Intensified Production Systems Impact on Nutrition (SIPSIN-IWMI) project and Bahir Dar Institute of Technology for funding the field research. The Innovation Lab for Small Scale Irrigation provided support for institutional engagement and supporting materials. 

Irrigation and agriculture development in Africa: Impact on water quality and ecosystem health in the Ethiopian highlands

https://oaktrust.library.tamu.edu/bitstream/1969.1/193986/1/tilahun-2019-tamu.pdf

Irrigation and agriculture development in Africa: Impact on water quality and ecosystem health in the Ethiopian highlands

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Irrigation and agriculture development in Africa: Impact on water quality and ecosystem health in the Ethiopian highlands

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Texas A&amp;M Repository

Texas A&M Repository