Water Resources NB (FINAL 19Dec2016)
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Contract number: 031A249A Work package number 4 December 2016 Deliverable 4.4.3 Water resources situation in the Ngerengere river basin Impact of land use change and water abstractions on the discharge of the Ngerengere river in Tanzania and its implications for agriculture and food security Meike Pendo Schaefer, Ottfried Dietrich Institute of Landscape Hydrology Leibniz Centre for Agricultural Landscape Research (ZALF) Müncheberg, Germany Public use Yes Confidenal use - - - 1 Inhalt 1. Introducon .................................................................................................................................................. 3 2. Overview of study area : gerengere river basin ......................................................................................... 4 3. Methodology ................................................................................................................................................ 5 Data basis....................................................................................................................................................... 5 Terminology and categori)aon .................................................................................................................... 6 Scenario approach ......................................................................................................................................... 7 S.AT model ................................................................................................................................................... 0 4. Current status of stream1ow in the gerengere river ................................................................................. 2 5. Main pressures a3ecng stream1ow in the gerengere river basin ......................................................... 10 Climate ......................................................................................................................................................... 10 5and use and land cover change 6575CC8 .................................................................................................... 10 .ater abstracons 6.A8 ............................................................................................................................. 13 6. Main driver of pressures in the gerengere river basin: populaon growth ............................................. 14 7. E:pected development of main pressures and impact on stream1ow in the gerengere river basin ...... 16 Climate ......................................................................................................................................................... 16 5and use and land cover change ................................................................................................................. 16 .ater abstracons ...................................................................................................................................... 17 Impact on stream1ow.................................................................................................................................. 17 0. Implicaons for agricultural food security strategies ................................................................................. 12 2. e:t steps ................................................................................................................................................... 20 Appendi: 1: Soil .ater Management Pracces 6S.MP8 ............................................................................... 21 References ....................................................................................................................................................... 23 2 Impact of land use change and water abstractions on the discharge of the Ngerengere river in Tanzania and its implications for agriculture and food security 1. Introduction Tan)ania lies within a )one of strong hydrologic changes and reportedly high pressure from driving forces such as populaon growth, agricultural sector development, and climate change 6Sch=fer et al., 20168. In many cases, this leads to growing pressure on natural resources, and water demand in some places already e:ceeds water availability, thus liming food producon and agricultural development 6Besada and .erner, 2015; GunaseAara et al., 20148. The gerengere river basin, which is located in the .ami/Ruvu catchment in South-Eastern Tan)ania, is no e:cepon to this case. Apart from climac changes, the main underlying causes of these changes are aCributed to water abstracons 6.A8 and land use/land cover change 6575CC8 6 atAhin et al., 20158. .ith regard to sustainable regional development and resource use, comprehensive Anowledge on water resources and the processes a3ecng them on drainage basin scale is of great importance. The following report draws on data and insights from two mulannual research proDects 6ReACCT and Trans-SEC, 2000-20168 focusing on the historic and current state of water resources, observed changes in hydrological parameters, and the correlaons with underlying main causes in the gerengere river basin. The described research aims at a8 an improved understanding of the relaon between stream1ow and 575C change, .A, and climate change in the gerengere river basin in Tan)ania. The gained insight shall be applied to b8 assess how future developments of the above pressures will a3ect discharge in the basin, thus c8 providing an assessment of e:pected impacts on agricultural development and food security strategies. Eindings will be specific for the Morogoro region, however, it is e:pected that some general statements can be derived and find applicaon in similar regions. The elaboraon and results of the worA are embedded in the Trans-SEC proDect, which aims at improving the food situaon for the most vulnerable rural poor populaon in Tan)ania through the idenficaon and disseminaon of successful upgrading strategies. All findings are shared with local authories and the proDect consorum. 3 2. Overview of study area : Ngerengere river basin The gerengere catchment is a sub- basin of the .ami-Ruvu river basin in Tan)ania and appro:imately 2,700 AmF large 6Eig.18. It covers the e:tent of the 154Am long gerengere river from its source in the 7luguru Mountains in the west to its Duncon with the Ruvu river near Mafisi village to the East 6GICA, 2013c8. Erom an elevaon of up to 2,260masl in the 7luguru Mountains, the topography of the catchment changes considerably towards the plains at around 300masl in the East 6Eig.28. Figure 1: Location of case study site The largest city in the catchment, Morogoro, is a centre of intense agricultural and industrial growth, and the region is e:emplary for environmental changes induced by these developments. These include land use and land cover change, increased surface and groundwater withdrawal, the building of dams and reservoirs, and degradaon of water Huality due to erosion and pollutants. Figure 2: The Ngerengere river basin in Morogoro, Tanzania The gerengere basin has been the site of ongoing hydrologic research for several years because it is spaally diverse, comparavely well researched, and Huite representave for developments and demographics found throughout Tan)ania 6see chapter 5 for further details8. 4 3. Methodology Data basis Type of Data Record Length Source Clima)c Data Measured 40 years .ami Ruvu Basin .ater OIce 6.RB.O, 61270-20108 2014a8; Tan)ania Meteorological Agency 6TMA, 6Precipitaon, 20138 Temperature, Re-Analysed 33 years The .EDEI Meteorological Eorcing Data Set Evaporaon8 6.eedon et al., 20148 61979J2012) ProDected 140 years The Inter-Sectoral Impact Model Intercomparison ProDect 6ISI-MIP8 6.ars)awsAi 61260-21008 et al., 20148 Measured discharge / stream+o, 60 / 40 years .RB.O 6.RB.O, 2014b8 61250-20108 Land use / land co er 1275, 1221, 5A DSAT images 6processed by S7A 6Mbilinyi, 1225, 2000, 201488 2005 Soil type data 2003 SOTERSAE - Soil database for Southern Africa 6DiDAshoorn, 20038 -istorical popula)on .gures 1267-2012 Census data 6EAO, 2016; GICA, 2013b; BS, 2006a; BS, 2006c; BS K OCGS, 2013; Regional CommissionerLs OIce Morogoro, 12278 Pro0ected popula)on .gures 2015-2035 ProDecon from census data 6GICA, 2013b; BS, 2006b; The .orld BanA, 20168 -istorical ,ater abstrac)on .gures 1225, 2010 .RB.O 6.RB.O, 2014c8 Pro0ected ,ater abstrac)on .gures 1275, 1221, ProDecon from .A data 2000, 2005 2010-2035 .RB.O / GICA 6GICA, 2013b8 Literature MaDor scienfic citaon databases 6.eb of Science, Scopus, Science Direct8 and some renowned non-peer-reviewed hydrologic publicaon databases 6Internaonal .ater Management Instute, Internaonal 7nion for Conservaon of ature8. 5 Terminology and categorization Classi.ca)on of landscape units Due to the high spaal heterogeneity of the gerengere river basin, the terrain was sub- divided into four landscape units based on similar parameters regarding elevaon, 575C paCern, populaon density, and number of river gauges with available data 6Eig.3 K Table 18. These landscape units are the basis for all proDecons and interpretaon of data and model results. Figure 3: Ngerengere ri er basin landscape units Table 1: 1 er ie, of landscape unit parameters Landscape E7tent Dominant L5LC Popula)on/8m 9 Ri er gauge s 5nit 38m94 3:ear 20054 3:ear 20124 Mighlands 200 Cropland, Eorest 300 Nonga, M orogoro 7rban 362 Cropland, Built -7p Area 451 Mindu Dam, Ningolwira Midlands 220 Bushland, .oodland 04 5uAwambe, Mgude 5owlands 1023 Cropland, Bushland 23 Dibundile, 7tari DPS2R model In order