Lake Manyara Watershed Assessment

Transcription

1 Photo/Greg Bevenger-USFS Lake Manyara Watershed Assessment Progress Report December 2003 Lake Manyara Watershed Assessment: Progress Report December

2 I. LAKE MANYARA WATERSHED ASSESSMENT Overview African Wildlife Foundation (AWF) has initiated a detailed assessment of the Lake Manyara watershed, which is one of two catchment basins that sustain the Tarangire-Manyara ecosystem, in northern Tanzania. Through a partnership with the U.S. Forest Service (USFS), AWF is working to protect forest, soil and water resources in important African landscapes, through its African Heartland program. To address concerns of habitat fragmentation and environmental degradation within the Lake Manyara watershed AWF has partnered with local stakeholders and the USFS to conduct an assessment of the watershed. AWF is leading the assessment, which includes development of a GIS and associated database, and compilation of relevant information related to the Lake Manyara watershed. USFS is providing technical assistance in watershed science, as well as financial support. AWF is building upon the considerable work that has already been undertaken by partners in the region 1, in order to improve the conservation of natural resources in this important landscape. AWF and USFS are conducting this assessment through a process that aims to characterize ecosystem elements from a watershed perspective, identify key issues and problems in the watershed, and ultimately provide management recommendations. Masai Steppe Heartland The assessment is being implemented through AWF s African Heartland program, which is a collaborative, landscape-level management approach to conserving Africa s unique wildlife resources. Heartlands are large areas of exceptional natural value where AWF works with a variety of partners, including local people, governments and other resource users to ensure these landscapes are prioritized for conservation and are kept ecologically and economically viable. The Tarangire-Manyara ecosystem comprises an area AWF calls the Maasai Steppe Heartland, which is a renowned area of global biodiversity value representative of east African woodland savannah. Lake Manyara is one of the key components of this Heartland and is recognized internationally as a Biosphere Reserve. Conservation Intervention in Masai Steppe Heartland AWF is working on a series of activities to protect the critical land units that connect and sustain this conservation landscape. This includes focused attention to key remaining corridors, dispersal areas, wetlands and catchments. Habitat fragmentation and environmental degradation are rapidly decreasing habitats and corridors available for wildlife in this landscape. Watershed health has implications for wildlife and their habitats throughout the Lake Manyara watershed. Lake Manyara itself provides critical habitat for aquatic fauna and birdlife with an exceptional number of birds, estimated at well over 380 species, including: lesser flamingo, greater flamingo, white pelicans, yellow billed storks, diurnal birds of prey, and 1 Organizations working on watershed management issues in the basin include: Institute of Resources Assessment (IRA), World Wildlife Fund (WWF), Tanzania National Parks (TANAPA), and IIED Drylands Program, among others. Lake Manyara Watershed Assessment: Progress Report December

3 white-necked cormorants. Lake Manyara also provides habitat for resident and migratory wildlife including elephant, buffalo, lion, hippopotamus, impala, giraffe, zebra, wildebeest, bushbuck, leopard, and baboon. (TANAPA, 2002) Lake Manyara National Park (LMNP) provides a variety of environments within its boundary. The combination and variety of landforms and vegetation types create a uniquely scenic landscape that is both diverse and ecologically complex. The principal features of the Lake Manyara area are the lake, flood plains and associated grasslands, groundwater forest, rift escarpment, acacia woodlands, Marang Forest and the hot water springs. (TANAPA, 2002) Wildlife in the Manyara basin depends on other areas and landholdings outside the national park. These areas include important wildlife habitat (Northern Highland Forest Reserve in the Ngorongoro Conservation Area, and the Marang and Esimingor National Forest Reserves), migration corridors (Kwakuchinja, upper Kitete, and Selela corridors), and important dispersal areas (Mto wa Mbu Game Controlled Area and the Ardai plains). Another area of importance for wildlife outside the park is the Manyara Ranch which is owned by the Tanzanian Land Conservation Trust (TLCT). Manyara Ranch represents an important piece of land in the Kwakuchinja wildlife corridor that connects Lake Manyara and Tarangire National Parks. Additional land holdings important for wildlife are community areas that surround the national park which are held by Maasai pastoralists and subsistence agriculturalists. Land use changes and human activities in the Lake Manyara watershed are having profound impacts on ecosystem health which affects wildlife conservation, National Parks, agricultural production, grazing regimes, and human livelihoods. Our watershed assessment is meant to provide a framework for guiding management of natural resources for the benefit of biodiversity and human inhabitants of the watershed. The information collected through this assessment process will assist AWF and its stakeholders in the following: land use planning and implementation; education in and adjustment to agricultural and grazing methods; adoption and enforcement of water laws where necessary; and improvement in forestry practices. Assessment Process AWF is using a watershed assessment process 2 that was developed by land managers in the United States and is being adapted to our work in Africa. A watershed assessment is a tool used to characterize the human, aquatic, riparian, and terrestrial features, conditions, processes, and interactions (collectively referred to as ecosystem elements ) within a watershed. It provides a systematic way to understand and organize ecosystem information. The process used for this assessment has six steps, which include: 1) characterization of the watershed; 2) identification of issues and key questions 3) description of current conditions; 4) description of reference conditions; 5) synthesis and interpretation of information; and 6) recommendations. 2 Ecosystem Analysis at the Watershed Scale: Federal Guide for Watershed Analysis Portland, OR, USA. Lake Manyara Watershed Assessment: Progress Report December

4 Current Status of Lake Manyara Watershed Assessment Along with our local partners and with inputs from the USFS, AWF is actively working on steps 1-6 of the assessment process. AWF has made progress in gathering existing physical and biological information and in developing a GIS project file for analyses of digital spatial data. Field reconnaissance commenced in December, 2002 when a USFS technical team accompanied AWF staff on a two week field trip to acquire more detailed knowledge on characteristics of the watershed. Through observations by the USFS team and further discussions with partners, we have a better understanding of threats affecting this system. As progress has been made with partners who are working in the region, it is becoming clear that much information already exists on the current conditions and problems affecting the watershed. In fact, through previous work by partners, concrete management recommendations have emanated from various assessments of the basin. Institutions and researchers have gathered and analyzed large amounts of primary data in order to formulate these prescriptions and in some cases implementation has commenced. A prime example of these efforts is the development of an Integrated Water Resources Management Plan for the Lake Manyara basin, which is being designed by water resources specialists at the Institute of Resources Assessment (IRA) at the University of Dar es Salaam. IRA has found that the prevailing system of uncoordinated water resources management in the basin cannot sustain the ever increasing water needs of the various expanding sectors, therefore a strategy must be sought to integrate the various sectoral needs against the available water resources in order to attain both economic and ecological sustainability. (Ngana, 2002) A number of constraints have been noted by IRA which inhibit sustainable water resources management including ignorance of water policies, lack of coordination between sectors, high in-migration rates into the basin, heavy in-migration of livestock, poor land use resulting in soil erosion and sedimentation, and the lack of a comprehensive database on water resources and water needs for: domestic, tourism, livestock, irrigation, wildlife and environmental flows. (Ngana, 2002) The aim of AWF at this stage is to conclude work on this assessment through formulation of management recommendations that can be implemented with partners working in this ecosystem. AWF will look for ways to add its comparative advantage in this area and to work closely with institutions such as IRA who are already developing the means to implement management actions that have emerged from previous assessments and this one. AWF will also continue compiling and synthesizing information that already exists and to add to it where possible, specifically through increased GIS data synthesis and through setting up a potential monitoring program in a targeted area of the basin. Lastly, we are planning to conduct an assessment of the Tarangire watershed, which along with Lake Manyara, makes up the Tarangire-Manyara Ecosystem. Because of the vast size of these two watersheds, it was decided to initially focus on Lake Manyara and conduct a detailed assessment of it. However, for a full understanding of watershed health in the Heartland, a parallel assessment needs to be conducted on the Tarangire watershed when funds become available. Lake Manyara Watershed Assessment: Progress Report December

5 II. WATERSHED ASSESSMENT PROCESS 1. Characterization of Lake Manyara Watershed The purpose of step 1 is to identify the dominant physical, biological, and human processes or features of the watershed that affect ecosystem functions or conditions. The relationship between these ecosystem elements and those occurring in the watershed is established. When characterizing the watershed, we identify the most important land allocations, land use practices, and regulatory constraints that influence resource management in the watershed. The watershed context is used to identify the primary ecosystem elements needing more detailed analysis. The Lake Manyara watershed extends approximately 766,710 ha within Mbulu, Monduli, Ngorongoro and Babati districts in Arusha Region of northern Tanzania. The boundaries of the basin form the watershed of the area drained by Lake Manyara. (Map 1.) It extends from 3.05 to 4.05 degrees south and to degrees east. The Lake Manyara watershed is part of the Maasai Steppe in northern Tanzania and part of the Tarangire- Manyara ecosystem. The following section provides a broad characterization of this watershed. Lake Manyara Watershed Assessment: Progress Report December

6 Map 1. Lake Manyara Watershed AWF has conducted field visits, held meetings with relevant partners, and compiled and collated existing information in order to characterize this watershed. In December, 2002, specialists from the USFS (Greg Bevenger, Hydrologist and Dan Svoboda, Soil Scientist) joined AWF for a week of field visits that focused on characterization of the Lake Manyara watershed and to begin identifying the current conditions and issues and key questions affecting this watershed. The team covered most areas of the watershed and was able to acquire detailed information from observations in the field. Many of the issues that have been identified in these preliminary efforts of characterizing the watershed and identifying the issues were further validated through the stakeholders workshop and through dialogue with partners who have been working on watershed issues in the basin. Summary characterization of the watershed has been established from stakeholder s workshop, field Lake Manyara Watershed Assessment: Progress Report December

7 reconnaissance, compilation of secondary data, and discussions with partners. The characteristics of the watershed include:? Evidence of land degradation is widespread throughout the drainage.? Disturbance of rangelands is evident; current grazing regimes are unsustainable; loss/disturbance of vegetative cover is severe in many areas of the watershed, affecting infiltration capacity and impacting the hydrologic cycle.? Wildlife/livestock carrying capacity needs to be understood.? Loss of forest cover is evident; critical catchment areas are under threat of encroachment from human activities.? Agricultural practices need to be improved to protect soil resources and maintain watershed integrity. 2. Identification of Issues and Key questions The purpose of step 2 is to focus the analysis on the key elements of the ecosystem that are most relevant to the management questions and objectives, human values, or resource conditions within the watershed. Key analysis questions are formulated from indicators commonly used to measure or interpret the key ecosystem elements. AWF and USFS hosted a stakeholder s workshop in order to gather relevant partners who are also working in the Lake Manyara watershed to help understand the issues and key questions affecting land management in this watershed. The gathering of partners and stakeholders to discuss the assessment was useful for hearing from local land managers and validating characterization efforts. One of the main focuses of the workshop was to identify and agree on the issues and key questions that are affecting the Lake Manyara watershed. Additional research has been undertaken from various colleagues and research institutions which have looked at the key issues affecting this basin. A compilation of information and results from AWF/USFS work in the basin, along with other efforts such as the IRA consultative workshop as presented at the Symposium 'Water Demand Management for Sustainable Development', Dar es Salaam, October 2002 can be summarized as the following: Key Issues Affecting Watershed Management: Lake Manyara Basin:? Lack of coordinated basin-wide water resources management strategy;? Lack of information on existing water sources, amount and quality;? Water use conflicts especially during the dry season between domestic water supply, livestock, wildlife, tourism and irrigation farming;? Over population, and significant in-migration;? Unsustainable land use practices: Inappropriate farming methods in the highlands e.g. Karatu and Mbulu and Babati Districts causing severe erosion and subsequent siltation to the rivers and lakes.? High concentrations of livestock especially during the dry season cause soil trampling and consequent soil erosion? Lack of knowledge on water resources policy and water rights: Lake Manyara Watershed Assessment: Progress Report December

8 ? Ineffective enforcement of conservation laws;? Lack of coordination between different sectors on natural resources management;? Baseline information needed on water sources, quantity and quality, and water uses by sector (i.e. domestic, irrigation, livestock, wildlife, tourism and environmental flows);? Carrying capacity of land resources to support the increasing population in the sub basin needs to be established; Lake Manyara Watershed Assessment: Progress Report December

9 3. Description of Current Conditions The purpose of this step is to develop information relevant to the issues and key questions identified in step 2. The current range, distribution, and condition of the relevant ecosystem elements are documented. Meteorology Precipitation Amount: Average annual precip = 650 mm mean annual precipitation recorded over a 26- year period ( ) at Lake Manyara. Other areas of the basin receive between 500 and 1,000 mm precipitation per year depending on relief Timing: divided over a short rainy season (November--January), and a long rainy season (February--April), prolonged dry period from June--October. Long-term variation in rainfall patterns results in fluctuation of the level of Lake Manyara. Air Temperature Average annual temp = approximately 22ºC. Extremes = The mean monthly temperatures do not deviate more than 3ºC from yearly mean. Surface Water Perennial streams: Simba, Kirurumo, Mto wa Mbu drain the Ngorongoro Highland Forest Reserve; Yambi river drains from the Marang Forest Reserve. Seasonal streams: Msasa, Endabash, Endala, Makuyuni The quality and quantity of river water depends on land use activities in the river catchments. Kirongozi and Mto wa Mbu rivers are relatively saline. The former and Makuyuni rivers are both very alkaline. Lakes/wetlands Lake Manyara: a brackish lake and perennial wetland, is approximately 40 km long by 13 km wide with maximum depth of about 2.0 m and part of the inland drainage system of northeastern Tanzania. The lake has ph values exceeding 10.8, and varies in size depending on rainfall and surface runoff in the catchment as well as discharge from perennial rivers. Available records show that in recent years, the lake dried up completely in 1921 and Ground Water Springs Miwaleni swamp, Abdul spring, Majengo spring, Jelule spring, Juma spring, Ngoro- Gunda spring, Mkini spring, Mzava s spring. Groundwater forest: springs exist at the northern tip of LMNP where a groundwater forest thrives on account of springs emerging from the foot of the escarpment. Drainage Basin Characteristics Watershed Morphometry Elevation range = 900 to 2,700 meters mean sea level Watershed size = 766,710 ha More information needed on morphometry including average watershed slope and aspect, stream reach gradients, channel types, stream channel erosion assessment. Soils Lake Manyara Watershed Assessment: Progress Report December

10 Four major soil groups: vertisols, calcimorphic, eutrophic, and ferruginous tropical soils Geology Crystalline basement rocks of precambrian age Volcanic deposits of Neogene age Ecological Zones Prins H.T.(1987), divided the park into 3 ecological zones or landscapes in accordance with main geological divisions: The rift valley bottom or lowlands The escarpment, including the foot slopes The uplifted Mbulu plateau or uplands Vegetation The main vegetation of the basin is classified in relation to the local drainage conditions including: Ground water forest and riverine Acacia woodland Thicket woodland Alkaline grassland Cynodon grassland Swamp Human Influence A population of approximately 350,000 pastoralists inhabits the Maasai Steppe ecosystem. They own a livestock population of approximately one million indigenous zebu cattle. The major ethnic groups in the project area are the Maasai, WaArusha, and Barbaig. The Maasai are the predominant ethnic group in the Kwakuchinja area. However, over the past 20 years there has been a large inmigration of other ethnic groups into the region modifying many of the traditional land and resource use practices. Due to the increase in immigration of nonpastoralists, and therefore increased competition for resource use, the Maasai are no longer able to meet their subsistence needs based solely on pastoral productions systems. This is one of the factors forcing the Maasai to change from a pastoral economic base to agricultural subdivision as a livelihood strategy. Pressure from the increasing human population, poorly planned land use practices (including farming and grazing in the surrounding areas) particularly from the villages on the escarpment, accelerate soil erosion Deforestation as a result of increasing demand for farming areas, trees for building houses, charcoal burning and lack of affordable alternative energy sources is creating barren lands and subsequent erosion and siltation. More data needed to assess level of degradation. The escarpment is harboring a number of tourist hotels and lodges, while the rapid growing small town Mto wa Mbu is full of shops and gallery shops and camping sites. There is controlled hunting in controlled game areas of Mto wa Mbu, and Kwakuchinja-Mbugwe. Data acquired further analyses needed Land use/land cover Satellite imagery Lake Manyara Watershed Assessment: Progress Report December

11 Limited meteorological data Major Data Gaps Tabular Data from weather stations Yearly, monthly, daily values Precip duration/intensity/frequency Streamflow data, lake levels Water quality data Water extractions Floral classification, vegetation DESCRIPTION OF ECOLOGICAL ZONES OF THE WATERSHED 3 1. Rift Valley Plains--Lake Manyara This area includes Lake Manyara and is characterized by flatlands, and undulating plains which range in elevation between m. Annual precipitation is 600mm and soils are brown-grey/brown clays. Vegetation is grassland, wetland, and moderately bushed grassland and forest. Land uses include subsistence pastoralism and ranching; wildlife conservation and tourism; subsistence dryland/irrigated farming; fuelwood collection; and small scale subsistence fishing. This region of the watershed is very important in that the entire basin drains into Lake Manyara, (Photo 1.) and land use activities throughout the watershed have the potential to negatively impact the lake. Major features of this area are a series of rivers that flow from the Northern Highland Forest Reserve, and Marang Forest Reserve. Near the headquarters of Lake Manyara NP and the town of Mto wa mbu, is the confluence of three rivers: Kirurumo R., Simba R., Mtowambu R. There is also a ground water forest at the entrance of the park. Inside the park there are seasonal rivers that flow off the escarpment into the lake which include the Msasa, Chem chem, and Endabash rivers. Also inside the park, the Yambi River, is a perennial stream flowing off the rift escarpment from the Marang Forest Reserve. Manyoca Village is just outside park boundaries to the south, where the local population is engaged in small-scale cultivation and limited fishing. Mining activities are also present here. Photo 1. Lake Manyara 3 The basis for the classification of these ecological zones comes from Mwalyosi s Integrated Resource Management Strategy for Lake Manyara Catchment Basin (1994), and AWF uses these zones as planning units when describing characteristics of the watershed as observed from field reconnaissance. Current information has been added to the characterizations of these zones, including digital photos which have been catalogued as annex 1. Lake Manyara Watershed Assessment: Progress Report December

12 2. Mbulu-Daudi-Endabash Area This area is on a hilly and undulating plateau, at an elevation of m. Annual precipitation is 800mm and soils are dark red loams/deep clays: Vegetation is broad leafed upland forest, thorn scrub, and bushland/grassland. Land uses here include large scale/subsistence farming; intensive subsistence pastoralism; forest reserve (Marang); timber harvest; and fuelwood collection. To reach this area, the team climbed up the rift escarpment from the southern end of Lake Manyara towards Mbulu town. This area has steep slopes and there was evidence of overgrazing (Photo 2.) and accelerated soil erosion on the hill slopes in the area. It is understood that burning is occurring on an annual basis in order to hasten growth of new grass for livestock. It was suggested by the USFS team that a burning regime that calls for less frequent burning could help protect the vegetative cover in this area, whereby increasing infiltration rates and decreasing erosion. Also, this area has seen significant deforestation with Marang Forest Reserve providing a reference condition of the forest cover that once characterized this area (Photo 3.). Another land use that is leading to degradation is the cultivation of steep slopes, with ineffective or non-existent terracing system. Lake Manyara Watershed Assessment: Progress Report December

13 Photo 2. Overgrazing in Mbulu We visited the Daudi ranger post on the edge of Marang Forest Reserve. The forest reserve seemed to be relatively intact and the integrity of the forest was good, according to a local ranger from the Forest Department. However, he explained that the edges of the reserve are facing threats from local communities for use of forest resources. Local people enter into the forest for collection of fuel wood, building materials, and other non-timber forest products. Lake Manyara NP is actually in the process of annexing this forest to be included as part of the park, which would elevate the protected status of this forest. Marang Forest represents a critically important area in this watershed and provides essential water catchment functions. Much of this area has been de-forested in the recent past, and Marang Forest Reserve provides a reference for what the forest cover was previously. Photo 3. Deforestation in Mbulu Area Lake Manyara Watershed Assessment: Progress Report December

14 3. Karatu-Mbulumbululand Area This area is flat to strongly undulating/rolling plateau with an elevation between m. Annual precipitation is 930mm and soils are red brown/brown vertisols, ferruginous tropical. Vegetation is thorn/scrubland. Land uses here include commercial large scale/subsistence farming; intensive subsistence pastoralism; and fuelwood collection. This well watered plateau is very suitable for agriculture and much of this area is under cultivation as well as used for agro-pastoralism. The team visited Rhotia village, Chem chem village and looked closely at the agricultural practices in use in this area. (Photo 4.) From a soil consvation standpoint, fields were rough tilled, and erosion breaks were present in some the fields. The presence of productive basalt soils are one reason for the level of agricultural productivity at this time. However a major concern was the amount of overgrazing that was observed, along with un-sustainable agriculture techniques. The current grazing regime on steep slopes along with intensive cultivation will drastically change storm response, by not allowing deep percolation and will severely affect groundwater recharge. This area is characterized by steep slopes in some areas and there was evidence of advanced soil erosion. (Photo 5.) Major movement of particles was seen on the steeper slopes with very course sediment load delivery to downstream areas. Over-grazing on top of cultivation in this area is having serious negative impacts and the sustainability of these systems is in jeopardy. Photo 4. Agriculture fields in Rhotia area Lake Manyara Watershed Assessment: Progress Report December

15 Preliminary discussion on potential strategies:? Plant crops/rows on the contour to break up overland flow; i.e. grass countours.? Leave residual stalks, agricultural waste i.e. maize stalks on field for erosion control? Adjust grazing regime? Zoning i.e. slope over 40% no agricultural crops grown; use for wood lots, or fuel production.? Grow woodlots on riparian areas.? Implement pilot restoration project on small watershed to show potential benefits, i.e. 400 acre watershed. Photo 5. Advaanced erosion in Rhotia area Lake Manyara Watershed Assessment: Progress Report December

16 Msasa/Marera River Further down in the watershed, towards the escarpment, the field team visited the confluence of the Msasa and Marera rivers. This channel has been highly disturbed (Photo 6.) through increased sediment delivery and from degradation of the riparian area. There was evidence of overgrazing in the riparian area with livestock using the entire length of the stream channel for watering, and the riparian area is completely denuded (Photo 7.). This stream channel has been significantly altered and there was evidence of destructive land use practices further upstream in the agricultural areas that we visited earlier. Photo 6. Msasa River Photo 7. Livestock use around Msasa River Lake Manyara Watershed Assessment: Progress Report December

17 This area highlighted the need for improved riparian management in many areas of the watershed. For example, in the case of this section of the Msasa River, use zones could be isolated for livestock watering points instead of letting cattle water along the entire length of the stream. 4. Crater Highland Forest This area is very mountainous and includes the Northern Highland Forest Reserve which reaches up to the rim of the Ngorongoro Crater. Elevation in this area ranges from m and annual precipitation is between mm. Soils here are brown/greybrown/red-brown ferrsols/eutrophic. Vegetation is broad leafed upland forest, wooded bushland and grassland. Land uses are forest reserve (Northern Highland), wildlife conservation and tourism, and subsistence farming. The Northern Highland Forest Reserve represents one of the most critically important catchment areas of the Lake Manyara watershed. This intact forested area provides much of the water that sustains the upper reaches of the watershed and ultimately flows to Lake Manyara. In the upper elevations, this tall forest environment represents a major water producing zone. This forest reserve is under threat from local subsistence activities. As part of the visit to this area, we were able to meet a forester from Ngorongoro Conservation Area Authority (NCAA) who is working with communities surrounding the forest reserve. Encroachment from human activities around the edges of forest by local communities is an issue and work is being done to protect the integrity of the forest reserve. As part of the watershed assessment, it was recommended by the USFS team that a survey of the forest be conducted and to undertake an inventory of the tree species in the reserve. Lake Manyara Watershed Assessment: Progress Report December

18 5. Makuyuni River Area This area is rolling and moderately dissected with an elevation ranging from m. Annual precipitation is mm and soils are brown clays. Vegetation in this area is bushed grassland. Land uses here include commercial dryland estate farming; subsistence farming; subsistence pastoralism; ranching; wildlife conservation and tourism; military activity; and fuelwood collection. This area is representative of much of the eastern part of the watershed and is characterized by extensive rangelands. A large part of the watershed drains from the eastern side of Lake Manyara and this area is a much dryer environment than the western and northern parts of the watershed. The environment here has less rainfall, the vegetation community is different, and the water cycle differs from that on the western side of the lake. The Makuyuni River drains this part of this watershed and the riparian condition of this stream is very poor, except when it flows through Manyara Ranch. The channel is very unstable and has been eroded away by accelerated erosion. Extreme overgrazing was observed in many of the rangelands that were visited. Maasai pastoralists use this area heavily and depending on the season and the availability of water, parts of these grasslands become overgrazed and highly degraded. This was demonstrated by the condition of the Loilera River area (Photo 8.) which clearly shows severe degradation and highly advanced erosion processes. There was widespread evidence of accelerated sediment delivery coming from all areas of the eastern rangelands, due to poor infiltration rates and disturbed vegetative cover. The water balance in this part of the watershed has been significantly altered due to changes in the vegetative cover from land use practices. Photo 8. Loilera River area advanced erosion processes Lake Manyara Watershed Assessment: Progress Report December

19 Manyara Ranch One area of the eastern rangelands/makuyuni area that has recently been brought under improved conservation management is the Manyara Ranch. This land unit provides a good comparison as a reference condition for the eastern rangelands in relation to the other areas that drain the Makuyuni River. Manyara Ranch is a 45,000 acre ranch that is being managed by the Tanzania Land Conservation Trust (with technical and management support provided by AWF) with a multiple use management approach for wildlife conservation and community development through livestock production and pastoralism. This area also represents a critical wildlife movement corridor, specifically between Tarangire and Lake Manyara National Parks. Through a comparison of the riparian condition of the Makuyuni River on Manyara Ranch and further upstream in the watershed, it is clear that grazing practices are severely impacting hydrological response in this area. In the areas upstream to the ranch, vegetation on the banks of the river has been disturbed and the river channel itself has been widened, demonstrating an unstable condition. (Photo 9.) This observation pointed to the need to take care of grazing issues in the areas further upstream in the watershed. Photo 9. Makunyi River disturbed riparian condition Conversely, the vegetation on Manyara Ranch and the riparian areas of the Makuyuni River on the ranch are in good condition (Photo 10.). This area is functioning well from a hydrological standpoint, due to adequate vegetation to soak up precipitation and allow adequate infiltration. The condition of the riparian areas on the ranch is much different as well. Trees and shrubs are important in holding the river banks together and the condition Lake Manyara Watershed Assessment: Progress Report December

20 of the riparian vegetation was extremely good. Range condition of the Manyara Ranch is different that the rest of the eastern rangelands and the ranch can be used to demonstrate a reference condition of a healthy rangeland. (Photo 11.) Photo 10. Makunyi River on Manyara Ranch intact riparian vegetation Photo 11. Range condition of Manyara Ranch Lake Manyara Watershed Assessment: Progress Report December

21 6. Kiru Valley-Babati Area This area is flatland/undulating plains, with an elevation of m. Annual precipitation is 750mm and soils are grey-grey/brown clays. Vegetation in this area is grassland, wetland, and moderately dense woodland. Land uses here include dryland/irrigated subsistence/commercial dryland estate farming; subsistence pastoralism; small scale fishing; mining; and fuelwood collection. Evidence of land degradation due to overgrazing was also seen in the Kiru valley. Similar to the areas in the eastern part of the watershed, the productivity and viability of these rangelands is under severe threat. The disturbance of the vegetative cover is significantly impacting the hydrologic response here. (Photo 12.) Photo 12. Babati Area disturbed rangelands Lake Manyara Watershed Assessment: Progress Report December

22 7. Ardai Plains This area is flatland/rolling to moderately dissected elevation of m. Annual precipitation is mm and soils are brown clays. Vegetation in this area is open grassland. Land uses here include commercial dryland estate farming; subsistence farming; subsistence pastoralism; ranching; wildlife conservation and tourism; military activity; and fuelwood collection. The Ardai Plains have been severely degraded and evidence of overgrazing and unsustainable land use practices in this area were obvious. Many of the same observations that were made in the section on the Makuyuni River area are applicable to this area as well. The plains are in the eastern part of the watershed and reach the watershed boundary almost to Arusha. Severe gully erosion can be seen in this area and the whole range of issues related to hydrologic response are evident here. (Photos 13-15) Photo 13. Ardai Plains Lake Manyara Watershed Assessment: Progress Report December

23 Photo 14. Ardai Plains Photo 15. Ardai Plains Lake Manyara Watershed Assessment: Progress Report December

24 Lake Manyara Watershed Assessment: Progress Report December

25 4. Description of Reference Conditions The purpose of this step is to explain how the ecological conditions have changed over time as a result of human influence and natural disturbances. A reference is developed for later comparison with current conditions over the period that the system evolved and with key management plan objectives. This section still needs additional work and analyses. One activity that is underway within AWF for this section is a land cover change analysis using three LandSat images over a time period of 20 yrs 1987 and 2000 and possibly add imagery from the 1970s, mid-1990s and possibly 2003 as well. This analysis will be completed by April, However, there has been previous work done in this area which has looked at environmental change in the basin using various techniques. The following information is an excerpt taken from the IIED Drylands paper titled A Profile of Environmental Change in the Lake Manyara Basin, Tanzania, produced by Rick Rohde and Thea Hilhorst. This paper is based on research conducted in association with the inter-disciplinary research project "Sustainable use of natural resources in rural systems of Eastern Africa Drylands: Strategies for environmental rehabilitation. The paper provides a good summary of environmental change that s taken place in the basin over that last one hundred years or so. One of the perspectives to emerge from this study is that the natural, social, cultural and economic landscapes of the Lake Manyara area are highly diverse and patterns of environmental change highly complex and localised. The area has a long history as a frontier zone, stretching back millennia. The rise and fall of Engaruka between the 13th and 18th centuries was a precursor to the population growth and development of irrigated settlements in the Rift valley today. The ebb and flow of hunter-gatherer, pastoral and cultivation activities within this environment over centuries have to a large extent modified and created the landscape which the pioneers and colonialists of the 20th century inherited. It was not a pristine wilderness or untouched 'garden of Eden' as some would like to believe. The history of frontier expansion by various groups of agro-pastoralists and cultivators over the last 100 years encompasses several phases of agrarian change associated with population growth, agricultural extensification and latterly, intensification associated with expanded markets and a more diversified economy. Similarly, the political economy of colonization, independence, Ujamaa, market liberalization and multi-party politics provoked unique and local responses which in turn can be traced in the environmental landscape. As a result, the Lake Manyara Basin has become ever more of a human landscape, side-by-side with its increasingly protected wildlife enclaves. To generalize about basin level environmental processes is inevitably to simplify and misrepresent. The impact which humans have had upon the environment is determined by complex factors including natural cyclic climatic events, combined with socio-economic conditions affecting land-use practices and marketing strategies. Evolving political circumstances that influence property and power relations between individuals and groups have also left their mark. Without a localized and historic perspective, landscape processes can all too easily be misinterpreted by researchers and planners. Lake Manyara Watershed Assessment: Progress Report December

26 Repeat ground photos, aerial photos and a comparison with colonial vegetation maps show that there has been very little change in the uncultivated parts of the arid and semi-arid plains lying to the east of the Rift Wall, which are associated with extensively managed pastoral activity. Also, evidence of changes in woody vegetation on the escarpment wall and its foothills demonstrates the rapid pace of natural patch dynamics in association with pastoral burning. Contrary to popular beliefs, this area appears to be least affected by increasing population pressures probably due to low and uncertain rainfall coupled with substrate and hydrological conditions. Undoubtedly, there are important problems elsewhere in the Lake Manyara area related to land degradation that are in urgent need of attention. Sheet and wind erosion, gullies and loss of soil fertility are a consequence of unsustainable land use practices but they can also be seen as an inevitable stage in the process of change from a predominantly pastoral/ pioneer zone to a populated agricultural landscape. There is also evidence of land use intensification where farmers and herders adapt to changing circumstances in a variety of ways. Most village councils that we met have developed bylaws to protect forests and other commonly used areas, although enforcement is often difficult. Those with a social and cultural connection to the land attempt to conserve natural resources sustainably, in spite of the many problems they face in surviving within an impoverished agricultural economy. While we have demonstrated that historical research methods can reveal important information about dynamic landscape processes, we must also admit their limitations. One of the many questions we have been unable to answer relates to massive gully formation, such as in the upper Makuyuni River catchment, near Kisongo. Are such gullies a sign of the beginnings of a long process of inevitable landscape degradation, or are the time-scales inherent in such landscape processes long enough to allow humans to adapt sustainable land-use practices in vulnerable areas? These and many other questions arise when analyzing environmental change in this basin. However, our analysis suggests that such radical degradation is limited to a small proportion of the Lake Manyara Basin and is confined to more recently settled marginal areas on fragile soils. Lake Manyara Watershed Assessment: Progress Report December

27 References: Sources of information for Lake Manyara watershed assessment AWF Spatial Analysis Laboratory (Nairobi). Ecosystem Analysis at the Watershed Scale: Federal Guide for Watershed Analysis Portland, OR, USA. Mwalyosi, R.B Institute of Resource Assessment Report: Integrated Resource Management Strategy for Lake Manyara Catchment Basin. IRA, University of Dar es Salaam. Mwalyosi, R.B., Yanda, P., Mungongo, C. and Ngana J.O Management Requirements for Sustainable Conservation of Lake Manyara and Lake Burungi Wetlands. Report prepared for WWF TPO and TANAPA. Ngana, J.O., Mwalyosi, R.B., Yanda, P., Madulu, N.F rd WaterNet/Warfsa Symposium Paper: Development of an Integrated Water Resources Management Plan for the Lake Manyara Sub Basin, Northern Tanzania. Dar es Salaam, Tanzania. Rohde, R After the Fall: Political Ecology and Environmental Change in the Lake Manyara Basin, Tanzania. IIED Drylands Programme, Edinburgh. Rohde, R. Hilhorst, T A Profile of Environmental Change in the Lake Manyara Basin, Tanzania. Research project: "Sustainable use of natural resources in rural systems of Eastern Africa Drylands: Strategies for environmental rehabilitation (SUNRISE). 22 Issue Paper 109, Drylands Programme, IIED Tanzania National Parks (TANAPA) Lake Manyara National Park--Draft General Management Plan. U.S. Forest Service Observations from Field Visit by USFS Technical Team; Greg Bevenger, Hydrologist; Dan Svoboda, Soil Scientist. Lake Manyara Watershed Assessment: Progress Report December