School of International Development University of East Anglia Are the rivers in Tanzania at risk of drying up? The contested causes of environmental change (Via the Usangu and Great Ruaha case study) Bruce Lankford Talk for the British Tanzania Society at SOAS 10th Oct 2016 Photo by B Lankford, 2000, Ruaha River just upstream of Usangu Wetland
Provisos! Expert knowledge/science/authority and public sociology (after Burawoy, 2004) regarding complex and long term environmental change in an area the size of ‘Wales’ but: • Risk of criticising others and placing myself as expert • Risk of contradiction; I too am facing ‘gaps’ in knowledge • Risk of painting a ‘ tableau ’ of fixed figurines, conditions and drivers. • Not been to Usangu since 2005 except for one brief visit 5 years ago. • Asked to reflect today as a 35 min public lecture. • This room contains many people with views, more recent and deeper knowledge. • Can only hint at ‘recommendations’ • Looking forward to the discussion.
Are rivers in Tanzania at risk of drying up? In a word: Yes (there is a risk). 1) Semi-arid area (Pe~650 mm; ETc 1900 mm) and ratio of irrigable land to water is weighted to the former. Excluding the peak flows of >150 cumecs in Jan-March, water supply during the rest of the year can feed approximately 80-90,000 ha of supplementary irrigation, and ~8,000 ha during the dry season. The irrigable area in Usangu can be estimated at 5 to 10 times this. 2) Increasing opportunities to withdraw small volumes of water that cumulatively add up. Via informal gravity intakes and small <3 to 5 kW diesel pumps with ~5-8 m suction . 3) Misinterpreting causes/impacts of hydrological change & drawing up seemingly-sensible/doable but flawed or blanket interventions that take us in unhelpful directions . E.g. fixed water rights, intake designs, drip, types of institutional support.
Location of case study in Tanzania – Gt Ruaha or Usangu Basin Area = 22,000 sq km Area of Wales = 20,761 sq km
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The sharing of water Watershed of the Usangu escarpment Runoff shared by many sectors
Smallholder irrigation and livestock/fishing Typically less than 500 ha, and sometimes fed by more than one intake , traditional or ‘modernised’
Large irrigation systems, > 3000 ha
Downstream water demands in the basin Ecosystems & livelihoods in Ihefu wetland - Usangu Ecosystems in the Ruaha National Park Hydropower for Tanzania: Kidatu dam
20,000 to 40,000 ha of irrigation varies according to rainfall. Measured in 1999 to 2005
Deforestation in highlands causing faster Interpreting plausible sanctioned causes of Ruaha change runoff response and lower baseflows of rivers. AND/OR Change in rainfall due to climate change Increasing area of rice irrigation ET; higher volumes consumed combined with narrative about inefficient irrigation. Excessive livestock numbers causing soil compaction, faster runoff and reduction in wetland’s ‘sponge’ ability to store water Wetland undergoing change due to upstream abstraction by irrigation and livestock impacts Power cuts are due to dams running out of water due to droughts and upstream abstraction of irrigation water
Insufficient evidence of deforestation affecting Critically investigated complexity causes of Ruaha change runoff. Alpine upland grass ecology Rainfall is semi-arid; highly variable Dynamic mosaic of wet and dry season irrigation ET; variable and unmeasured efficiencies; water recycled; dry season impact is relatively greater; role of intake modernisation and water rights. Livestock numbers might cause local environmental change but insufficient to alter catchment hydrology at the volumes seen. Difference from reported high numbers of game reported historically. Past flood events deposited detritus; wetland channels blocked; expands and evaporates more; leading to lower flows at exit for a given inflow of water; fewer large fauna clearing passages Power-cuts were fault of dam operation. Excessive rapid draw-down of dam storage under political pressure to generate more/ cheaper electricity. = inability to bridge dry periods.
Zero flows in RNP and HEP cuts not directly connected Water Resources Engineering Programme (WREP, UDM) Power cuts during 1990 to early 2000s were due to a combination of a) political pressure to generate electricity/revenue but not conserve water behind Mtera storage dam and b) the two dams Mtera and Kidatu not being operated as a single unit after turbines were installed at Mtera in 1998 Similarities with lake Albert and Owen Falls dam in 2005 http://reliefweb.int/report/kenya/usda-low-water-levels-observed-lake-victoria
Note log scale 1000 Supply hydrograph Supply hydrograph, 1998 1970 to 1990 onwards – difference due to upstream abstraction In a dry year, river still flows in the wet season 100 Supply and demand (m 3 /sec) 10 1.0 0.1 Dec Jan Dec Jan Dec Jan Dec Jan Time
Irrigation 472 Mm 3 Beneficial non- process depletion Domestic 2.5 Mm 3 Beneficial (Wetland evaporation) process 379 Mm 3 Livestock 3.5 Mm 3 depletion 478 Mm 3 Available 1200 Mm 3 Non-beneficial depletion Gross Inflow 3700 Mm 3 (irrigation losses) Net Inflow 3330 Mm 3 343 Mm 3 Basin water accounting = human- process depletion / net inflow Outflow 2130 Mm 3 (478 + 343) / 3330 = 25% So ¼ of water (in 2005) consumed upstream of Usangu wetland Groundwater 370 Mm 3 Committed (to hydro-power, which To East African Rift also serves Ruaha National Park Valley geology and fault and Kilombero Sugar)
Zero flows in RNP and HEP cuts not directly connected RIPRWIN report on Mtera, 2005 “These findings lead to the conclusion that the problems at Mtera and Kidatu may be attributed more to water management at Mtera than on any other factor including drought. The control and regulation of abstractions operations that are conducted in the Great Ruaha River Catchment upstream Mtera reservoir are more important to keeping the level of the Utengule swamp high enough to sustain flow in the Ruaha National Park and therefore more beneficial to the Park than to Mtera reservoir. The rainy season during December to April is the best for filling the Mtera dam and not the dry season. From these findings, RBWO are convinced that if the reservoirs are operated modestly and according to prudent operation rules these crises and events can be minimized considerably. “
More recent errors in science? Next few slides – comparing surveys from the World Bank with those undertaken by SMUWC an RIPARWIN
Satellite data shows the staggering expansion of informal irrigation in the upper GRRC Large-scale schemes of Mbarali, Kapunga and 1998 2013 Madibira Planned small-scale Unplanned schemes irrigation development Source: World Bank Group, unpublished report (2015) 19
20,000 to 40,000 ha of irrigation varies according to rainfall. Measured in 1999 to 2005
Next few slides – responding in two ways to concerns about excessive upstream consumption by irrigation. 1) Improving the efficiency of irrigation 2) Regulating water demand via the application of water rights.
Engaging with irrigators Top-enders Tail-enders Collective arrangements October 11, 2016
Water management for a rice nursery at the top-end of the irrigation system Water management for a rice nursery at the tail-end of the irrigation system
Engaging with irrigators Replacing this type of ‘support ‘thinking “Farmers must be trained on soil and water technologies to enhance crop production and food security” ASARECA. 2006 Maputo Workshop statement www.asareca.org/swmnet . With this kind of support thinking: What training, institutional and technological needs arise when we bring farmers from top- and tail-end systems together while handing them responsibility to allocate water between themselves within irrigation systems, and between systems and to downstream users?
Water rights – World Bank Project RBMSIIP, 1998- IWRM; formal water rights, expressed in flow rate for abstractors of water for productive uses – consists of an application fee of $40, then $35 flat rate/year, then $0.035 per m 3 per year. Rationale for introducing water rights: “enhancement of water fees... as an incentive for water conservation... and as a source of funds for water regulation activities, catchment conservation and water resources monitoring” “economic instruments include water pricing, charges, penalties and incentives to be used to stimulate marketing mechanisms and serve as an incentive to conserve water..”
Local artisans and traditional intakes – consider form and function October 11, 2016
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