1 2 WATER ATLAS of the Wami/Ruvu Basin TANZANIA 3 Copyright© Global Water for Sustainability Program - Florida International University This publication may be reproduced in whole or in part and in any form for educational or non-profit purposes without special permission from the copyright holder, provided acknowledgement of the source is made. No use of the publication may be made for resale or for any commercial purposes whatsoever without the prior permission in writing from the Florida International University- Global Water for Sustainability Program. Any inquiries can be addressed to the same at the following addresses: Florida International University Global Water for Sustainability Program Biscayne Bay Campus 3000 NE 151 St. ACI-267 North Miami, FL, 33181 USA Email:[email protected] Website: www.globalwaters.net For bibliographical purposes, this document should be cited as: GLOWS - FIU 2014. Water Atlas of Wami/Ruvu Basin, Tanzania. 117 p. ISBN 978-1-941993-01-9 Disclaimer This document is made possible by the generous support of the American people through the United States Agency for International Development (USAID). The contents are the responsibility of FIU/GLOWS and do not necessarily reflect the views of USAID or the United States Government. 4 Acknowledgements This project has been funded by the American people through USAID. This project was implemented jointly with the Wami/Ruvu Basin Water Office with support from the Basin Water Board and the Tanzanian Ministry of Water- Directorate of Water Resources. Contributors: Amartya Saha, Mercy Asha Mohamed, Mwasiti Hassan, Rosemary Masikini, Maria Donoso, Vivienne Abbott and Elizabeth Anderson. Sources of Data: The Wami/Ruvu Basin Water Office (Morogoro), Ministry of Water, Tanzania, provided data on rainfall, river discharge, water level, geology, hydrogeology, administration, infrastruc- ture and population demographics. Data was obtained from the Wami/Ruvu Basin Water Resources Management and Development Study carried out by JICA and made available through the Wami/Ruvu Basin Water Office. ClimateWizard has provided map layers for climate predictions (temperature, precipitation and evapotranspiration) run for the Wami/Ruvu basin based upon a basin boundary shapefile uploaded to the web interface (http://www.climatewizard.org) 1 km resolution Evapotranspiration raster datasets for the region were obtained from the NASA MODIS Global Evapotranspiration Project run by the Numerical Terradynamics Simulation Group at the University of Montana. (http://www.ntsg.umt.edu/project/mod16#data-product). Digital Elevation Model (30m resolution, ASTER DEM) was obtained from NASA and Japan Space Research Organization. Landsat images of the Wami/Ruvu basin region from 1984-2012 were obtained from Time and Google Earth via the online interface (http://world.time.com/timelapse/). Forest cover change (2000-2012) images based on Landsat image analysis were obtained from Google Earth Engine and Hansen et al. 2013 via the web interface (http://www. earthenginepartners.appspot.com/science-2013-global-forest). Source: Hansen/UMD/Google/USGS/NASA Data of threatened amphibian, reptile and mammal species were obtained from the IUCN web interface (http://www.iucnredlist.org/) Rivers of theWami/Ruvu Basin were digitized from Google Earth 2013. All maps have been created using ArcGIS 10.2 unless specified otherwise. Design: Alejandro Abramovich 5 Contents 1. The Wami/Ruvu Basin at a glance 12 2. Physical features, topography and lithosphere 34 2.1 Physical landscape 34 2.2 Geology of the Wami Basin 42 2.3 Geology of the Ruvu Basin 42 3. Ecosystems: forests, wetlands and biodiversity 46 3.1 Forests, wetlands and water resources 46 3.2 Ecosystems and biodiversity 53 3.3 Riparian/gallery forests and biomonitoring of stream ecosystems 55 3.4 Estuaries 56 4. Climate: trends and projections 62 4.1 Temperature 63 4.2 Precipitation 66 4.3 Evapotranspiration 74 6 5. Water resources 80 5.1 Surface water resources: sub-basins, rivers, wetlands and reservoirs 80 5.2 Groundwater resources and hydrogeology 90 6. Water resources use 96 7. Vulnerability of water resources 102 7.1 Groundwater extraction 104 7.2 Flood-prone areas 105 7.3 Deforestation, soil erosion and earlier drying up of streams 107 7.4 Adaptation 112 References 114 7 Index of Maps 1. The Wami/Ruvu Basin at a glance 12 Map_1_1: Location of the Wami/Ruvu Basin in Tanzania, Africa, page 14 Map_1_2: Topography, subcatchments and cities, page 15 Map_1_3: Administrative regions and towns, page 16 Map_1_4: District wards (2002 Census), page 17 Map_1_5a and b: Districts 2002 Census and 2012 Census, page 18, 19 Map_1_6: Population of wards (2002 Census), page 20 Map_1_7: Population density at the ward level (2002 Census), page 21 Map_1_8a: Water availability (%households with access to improved water source) and infant mortality, page 25 Map_1_8b: Life expectancy and infant mortality, page 26 Map_1_9: Transportation, roads, rail, bridges, page 27 Map_1_10a to d: Land cover, page 28-33 2. Physical features, topography and lithosphere 34 Map_2_1: Landforms of the Wami/Ruvu Basin, page 36 Map_2_2: Western Wami/Ruvu Basin topographic map, page 37 Map_2_3: Northern Wami/Ruvu Basin topographic map, page 38 Map_2_4: Eastern Wami/Ruvu Basin topographic map, page 39 Map_2_5: Southern Wami/Ruvu Basin topographic map, page 40 Map_2_6: Subcatchments of the Wami/Ruvu Basin, page 41 Map_2_7: Soil classification of the Wami/Ruvu Basin, page 43 Map_2_8: Geology of the Wami/Ruvu Basin, page 44 Map_2_9: Geological Lineaments of the Wami/Ruvu Basin, page 45 3. Ecosystems: Forests, wetlands and biodiversity 46 Map_3_1: Forest reserves, national parks and wetlands, page 47 Map_3_2: Forest reserves, national parks and wetlands with topographic map, page 48 Map_3_3: Forest reserves, national parks and wetlands in the western Wami/Ruvu Basin, page 49 Map_3_4: Forest reserves, national parks and wetlands in the northern Wami/Ruvu Basin, page 50 Map_3_5: Forest reserves, national parks and wetlands in the eastern Wami/Ruvu Basin, page 51 Map_3_6: Forest reserves, national parks and wetlands in the southern Wami/Ruvu Basin, page 52 Map_3_7: Wami and Ruvu estuaries, page 57 8 4. Climate: trends and projections 62 Map_4_1: Isohyets showing annual rainfall averaged over 1950-2010, page 67 Map_4_2: Rainfall stations and annual average rainfall isohyets averaged over 1950-2010, page 68 Map_4_3: Rainfall stations and elevation, page 69 Map_4_4: Projected annual precipitation for the 21st century by an ensemble of 16 General Circulation Models, page 70 Map_4_5 to Map_4_10: Seasonal Variation in evapotranspiration (ET), page 75 Map_4_11: Evapotranspiration in the year 2000 at a 1 km resolution, page 76 Map_4_12: Evapotranspiration in the year 2012 at a 1 km resolution, page 77 Map_4_13: Potential evapotranspiration (PET), page 78 5. Water resources 80 Map_5_1: Surface water resources of the Wami/Ruvu Basin and sub-basins: rivers, wetlands and reservoirs, page 81 Map_5_2: Hydrological monitoring stations and annual rainfall, page 82 Map_5_3: Hydrological monitoring stations and basin topographic elevation, page 83 Map_5_4: Rainfall and hydrological monitoring stations in different sub-catchments of the Wami/Ruvu Basin, page 84 Map_5_5: Surface water reservoirs in the Wami/Ruvu Basin against a backdrop of average annual rainfall, page 85 Map_5_6: Aquifers and water yield in the Wami Ruvu Basin, page 92 Map_5_7: Drilled depth and Static Water Level, page 93 Map_5_8: Static Water Level isocylines and wells, page 94 Map_5_9: pH in the Wami/Ruvu Basin, page 95 6. Water resources use 96 Map_6_1: Water user permit locations in the Wami/Ruvu Basin in 2012, page 98 Map_6_2: Irrigation user permit locations as of 2012, page 100 Map_6_3: Mechanized and non-mechanized agriculture, page 101 7. Vulnerability of water resources 102 Map_7_1: Borewell locations along with pumping capacity against a backdrop of average annual rainfall (1950-2010), page 104 Map_7_2: Borewell locations and yields against a backdrop of projected annual rainfall (2014-2040), page 104 Map_7_3 Forest cover change in the Wami/Ruvu Basin (2000-2012), page 109 Map_7_4: Forest cover loss in the Wami/Ruvu Basin (2000-2012), page 110 9 Foreword: a picture is worth a thousand words... The role of spatial information in water resources management Water resources management requires linking togeth- give a two-dimensional sense of the physical features of Such a map of hydrographs is useful to compare the dis- er hydrological, ecological, socioeconomic and water a region. The middle map displays the spatial concentra- charge in different tributaries and locations in the river demand information, all of which are spatial by nature. tions of groundwater borewells against a map of an- basin. For instance the headwaters of the Ruvu basin (left For example there are high rainfall areas and arid zones, nual rainfall. Notice the clustering of borewells on the side of the map) have discharge ranging from 0.5—12 rainforests and deserts, agriculture and urban areas, high left and right sides of the map, corresponding to an arid m3/s. Flow increases downstream until the last station, population density and water demand, and so on. Dis- area (hence high groundwater use) and urban area. Such 1H8A shows discharge between 40 –150 m3/s. Such a playing these different sets of information on maps en- a map can indicate the need to regulate the number of map also indicates seasonal patterns of flow. The highest ables the viewer to observe patterns and connections borewells and daily amount of groundwater extraction flow is seen to occur during the main rainy season be- existing between them and thereby understand the in- for sustainable groundwater use. The map on the right tween March and May. Headwater rivers have the high- formation better. The ability to view information spatially shows population density at the ward level, which pro- est flow in March-April, whereas stations downstream using maps thus enables the accurate assessment, plan- vides an idea of domestic water demand. see a lag of around 1 month in peak discharge.