Irrigated agricultural ecosystems in Africa Timothy O. Williams Director, Africa International Water Management Institute (IWMI) WLE/IWMI Workshop on Unlocking Value from Public Large Scale Irrigation Systems, Negombo, Sri Lanka, 7/4/2015

Presentation Outline Introduction Review of ecosystem impacts of irrigation New drivers of irrigation – opportunities & challenges Researchable priorities in ecosystem-inclusive management of irrigation in Africa

Introduction Irrigated agriculture, an ecosystem management activity. Mosaic of irrigation systems in Africa. Diverse irrigated agroecosystems with great variability within and between systems.

Introduction (continued) Irrigation has been promoted primarily to meet food security and economic development objectives, with ecosystem concerns considered secondary. Poor understanding of linked social-ecological systems that irrigated agroecosystems represent. Short-term perspectives of decision makers.

Basin Irrigation potential (‘000 ha) Environmental impact hazard SalinityHealthForestFisheryWildlife Senegal River Niger River2, Lake Chad1, Nile River8, Congo/Zaire River 9, Zambezi River3, Okavango Limpopo River Mediterranean Coast Environmental impact assessment of irrigation by basin in Africa Source: FAO, serious; ++ moderate; + low or nil

Impact categoryWonji/Shoa, Ethiopia Finchaa Valley, Ethiopia Senegal River Quality of irrigation water Good, with no risk for irrigation purposes Saline water Hydrology Rising of groundwater table High surface runoffSea water intrusion Change in soil properties Damage to soil structure and soil crusting Soil degradation due to sediment deposits from hills Soils exposed to increasing salinity Downstream water quality Affected adversely by agrochemicals used in irrigated agriculture Increase in water table salinity Surrounding ecosystems n.a.Natural vegetation cleared Proliferation of aquatic weeds; reduced flooding and dikes for irrigation have reduced traditional grazing land Environmental impact analysis of large-scale irrigation schemes in Ethiopia and Senegal River Sources: D. Ruffeis et al. (2008); DeGeorges and Reilly, 2006; Dumas et al. (2010)

Impact categoryWonji/Shoa, Ethiopia Finchaa Valley, Ethiopia Senegal River Quality of irrigation water Good, with no risk for irrigation purposes Saline water Hydrology Rising of groundwater table High surface runoffSea water intrusion Change in soil properties Damage to soil structure and soil crusting Soil degradation due to Soils exposed to increasing salinity Downstream water quality Affected adversely by agrochemicals used in irrigated agriculture Increase in water table salinity Surrounding ecosystems n.a.Natural vegetation cleared Proliferation of aquatic weeds; reduced flooding and dikes for irrigation have reduced traditional grazing land Environmental impact analysis of large-scale irrigation schemes in Ethiopia and Senegal River Sources: D. Ruffeis et al. (2008); DeGeorges and Reilly, 2006; Dumas et al. (2010)

Potential environmental impacts of SSISs Excessive groundwater extraction leading to land subsidence. Gully erosion and desiccation of dambos/fadamas, particularly in intensively utilized dambos in dry areas e.g. Kano Basin in Northern Nigeria and the communal lands in Zimbabwe.

Summary of ecosystem impacts of irrigation in Africa Lack of detailed studies and baseline data to rigorously assess ecosystem services associated with irrigation and impacts of irrigation on surrounding ecosystems. There is evidence that irrigated agriculture, particularly LSISs, have led to adverse impacts on surrounding ecosystems. The confounding effects of natural or other anthropogenic stressors are not often evaluated.

Summary of ecosystem impacts of irrigation in Africa (continued) Detailed analysis of impacts of SSISs on ecosystems and ecosystem services still lacking. Is there an irrigation scale effect on ecosystem services provided and impact on surrounding ecosystems?

A resurgence of interest in irrigation in Africa A World Bank (WB) initiative to increase the area under irrigation in 6 Sahelian countries from the current 400,000 ha to 1million ha by 2020 at a cost of $7 billion A WB loan of $400 million to revitalize LSIS and transform irrigation management in Nigeria New private sector commercial LS and MSISs in Ghana, Nigeria, Tanzania and Zambia

A resurgence of interest in irrigation in Africa Why? Why now? What are the new drivers, opportunities and challenges?

9.5 billion people by 2050

Source: FAO, 2014

Research questions What are the basic incentives and disincentives for ecosystem-based management of irrigation? What are the challenges of ecosystem-based management of irrigation for long-term food security, poverty alleviation and economic development? What practical and politically feasible policies and strategies are needed to enable transition towards ecosystem-based management of irrigation?

Research will be needed to: Improve knowledge of the whole range of ecosystem services associated with irrigation – their values and costs. Determine and differentiate the impacts of other natural and anthropogenic stressors from the impact of irrigation.

Research will be needed to: Identify economic instruments and innovative financing mechanisms that can allow the application of ecosystem-based irrigation management. Monitor long-term changes in irrigated agricultural ecosystems from a basin perspective.

Thank you for your attention