Bastable, H.G.

Calder, I.R.

English

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institute ofHydrologyI SNatural Environment Research CouncilCentre for Ecology and HydrologyComponent Instituteslosm“e of rf ethwater EcologyIrsofu:e oi HydrologyInstinne of Teo al Loa1o/3yErstitue of Viro!ogy & Lvoroninenal Microbto!ogyNatural Environment Research Councila•••A Institute of, JJHVdrology••••COMMENTS ON THE MALAWI GOVERNMENTWATER RESOURCES MANAGEMENT POLICYAND STRATEGIES•• IRCalder & H G Bastable•Hydrology Adviser to the British Overseas Development Administration••••Institute of HydrologyCrowmarsh GiffordWallingfordOxfordshireOXIO 8BBUnited Kingdom•Tel: 0491 838800Fax: 0491 832256Telex: 849365 HYDROL G••••••••••••••••••••••••••••••••••SUMMARY1. The Water Resources Management Policy and Strategies document provides sound and wellargued reasons for developing a Water Resources Management Policy in Malawi.2. These arguments could be strengthened with respect to consideration ofthe sensitivity of the Lake Malawi - Shire River system to both natural and man inducedchanges.3. The issue of sensitivity is considered in relation to the following:* FUTURE WATER RESOURCE ALLOCATION - A ROBUST OR FRAGILERESOURCE?* SENSITIVITY ANALYSIS* MANAGEMENT OPTIONS••••••••••••••••••••••••••••••••••FUTURE WATER RESOURCE ALLOCATION - A ROBUST OR FRAGILERESOURCE?•It is well recognised that the economy and future development potential of Malawi isinextricably linked to the continued functioning, both in terms of waterquality and quantity,of the Lake Malawi - Shire River system. It is also widely believed that"Malawi is endowedwith abundant water resources"; with Africa's third largest freshwater lake within the countryboundaries it is easy to understand this sanguine view.The present functioning of the system does not necessarily imply it will continue into thefuture. For two decades this century them was no flow out of the Lake; a result almostcertainly due primarily to natural climatic variability. If the climatic situation was to repeattoday the impact wouldbe severe; electric power production would cease,transport on the lakewould be brought to a virtual halt through lack of port facilities, touristdevelopments on thelake shore would be badly affected a.s would water supplies to the major city and townssupplied by the Shire together with the irrigated production of sugar cane fed lower down theShire. In the longer term there would be adverse impacts on fisheries and the environment.SENSITIVITY ANALYSISThe sensitivity of the system to changes in land use with respect to the area of the landcatchment under forestry and the area under irrigation has been investigatedusing a previouslydeveloped water balance model for Lake Malawi (Calder et al. 1994).Figure 1 shows the observed lake levels since 1955together with the predicted levels obtainedusing a model which takes into account a 13% reduction in natural forest cover during theyears 1967-90. Figure 2 shows that if the 13% reduction in forest cover had not occurred thepresent lake levels be about I m lower than they are.Figures 3 and 4 show how lake levels in the recent past would have been affected had theybeen operating under different irrigation scenarios. The Water Resources Management Policygives a figure of 44,6000 ha as the present areaunder irrigation for sugar and rice with thepotential of 100,000ha for small scale self-help irrigation schemes. Figure 3 shows the effectson lake level of a worst case scenario in which it is assumed that (i) a similar area wasdeveloped for irrigation in Tanzania, giving a total arca under irrigationof 300.000 ha. andthat (ii) all these schemes fell within the lake catchment area and that (iii) the demand figureof 2.5 m depth of water is consumed per hectare (SADC conference 1994). Using the samearca under irrigation but assuming what is thought to be a more realistic figure of 1m as dmextra annual evaporation from an irrigated area the effecuson lake levels arc less, Figure 4.•••2••••••••MANAGEMENT OPTIONSAt present our ability to forecast climate variability and change is very limited, and thepossibilities for controlling climate change virtually non existent. lhere are however twooptions for reducing the impacts of such a repeat of climatic conditions,disaster preparednessand integrated water resource management.•Disaster preparedness.Disaster preparedness would involve having in place alternative plans forelectrical generation.water supply and transport, should these systems be affected, and to use the zero cost optionwhen considering alternatives for future developments which do not relyon continuous Shireflows.Integrated siater resource management.Integrated water resource management should ensure that, even if theclimatic conditions didrepeat, the effects on the Lake Malawi- Shim River system were not worsenedby man inducedchanges and developments.A central theme of Malawi's water resource planning should be directed,as far as is practical.towards maintaining outflows from the Lake.It was recognised at the SADC conference on Integrated Water Resources Management forthe Zambezi (SADC, 1994) that, for the Zambezi region as a whole, the three most importantdevelopment activities which influence the water balance are, in order of importance:irrigation, hydropower and land use change (industrial use and domestic supply areinsignificant and likely to remain insignificant into the foreseeable future compared with theeffects of these major three developments). Within Malawi, although hydropower generationis a major industry it is not a consumptive user of water. There arcno major impoundmentreservoirs, in place or planned, which give rise to higher evaporative losses as is the situation.for example, for Cabora Bassa and Kariba.The developments which willmost affect the waterbalance of the Lake Malawi-Shim River system arc therefore irrigation and land use change.The regulation of irrigation schemes, and land use changes which reduce flows, particularlywhere these effect flows to the lake rather than the Shire River, requiresa pricing policy forwater which takes account of the value of water to stakeholders at different stages of itsmovement through the system.Pricing policy. The value of water decreases as it moves through the system. Water whichis at high altitude on the land catchmcnt of the lake has the potential for generating electricitybefore it reaches the lake, sustaining lake levels which support the fisheries,and transport, andthe tourist industry, can be used for hydroelectric generation after leaving the lake and forirrigation or supply purposes lower down the Shire. Water in the Shire before exiting to•3Mozambique has environmental value for sustaining fisheries and wildlife but has few of theother economic benefits. Pricing policies will need to be developed such that where these usesreduce flows to the system the charge to the developer reflects the losses incurred by the otherdownstream stakeholders.•Pricing policy - irrigation water. In practice this should mean that the charge to the irrigatorof water for irrigation purposes on the land catchment of the Lake should be substantiallyhigher than that for water taken from the outfall of the Lake, which itself should be higherthan that taken from the lower Shire below the hydropower schemes. Such a charging policyis likely to shift the balance of future major irrigation schemes to the Lower Shire exceptwhere the returns from cash crops or reduced transportation costs can offset the higher watercharges.•Regulatory (Pricing) policy - land use. Land use has an influence on the water balance ofthe system. It is known from studies carried out worldwide that forests, whether man madeor natural tend to evaporate more water than agricultural crops. Modelling studies of the waterbalance of Lake Malawi (Calder et al. 1994) confirm that Malawi is not an exception to thisgeneral rule. The conversion of the indigenous miomba woodland to annual agricultural cropssuch as maize will increase flows to the system, conversion of agricultural land to plantationforestry will have the opposite effect. A land use policy should take account the economicreturns from forestry in relation to the extra consumptive use charged using the price of waterat the position in the catchment where it is consumed.A methodology which should assist the development of a pricing policy is the combinationof water balance modelling and sensitivity analysis. By altering the proportions of land underdifferent land uses or under irrigation within a watcr balance model the effect on lake levelsand outflows can be calculated and eventually translated into economic costs to thedownstream stakeholders.4••REFERENCES• Calder,I.R.,Hall,Rt., Bastable, Gunston,H.M.,Shela,0, Chirwa,A. (1994).Theimpactof landusechangeonwaterresourcesin sub-SaharanAfrica: A modellingstudyofLakeMalawi. To besubmittedto J.Hydrol.•SADC(1994).Reporton theLivingstoneworkshop.In preparation.••••••••••••••••••••••5•••••••••••••••••••••••••••••••••LakeMalawi-predictedandobservedlakelevelsassumingdecliningforestcoverbetween1967-90477E476ObservedPredicted0474_0 Co >4730 as472471	19501955196019651970197519801985199019952000	Figure1Time(years)ewesee••••••••••••••••••••••••••••LakeMalawi-predictedandobservedlakelevelsassumingacatchmentforestcoverof64%477E476E DObserved_Predicted-Ed475"0 a) > o474sa ca a)>473a)cl)co472—J471,,	19501955196019651970197519801985199019952000	Figure2Time(years)•11••••••••••••••••••••0•••••••••••LakeMalawi-predictedandobservedlakelevelsassumingannualabstractionof7.5x109M3477ObservedE476-le475a) o474Cd a) >473----------a) a) m472_1471	19501955196019651970197519801985199019952000	Figure3Time(years)Predicted11111P••••••••••••••••••••••••••••••LakeMalawi-predictedandobservedlakelevelsassumingannualabstractionof3.0x109 m3477a)co472—_IObservedPredictedE4764eEs475-o a) o474CLIa)>473471	19501955196019651970197519801985199019952000	Figure4Time(years)

Comments on the Malawi Government Water Resources Management Policy and Strategies

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Comments on the Malawi Government Water Resources Management Policy and Strategies

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