Assessing the Hydrology of a Data-Scarce Tropical Watershed Using the Soil and Water Assessment Tool: Case of the Little Ruaha River Watershed in Iringa, Tanzania

The hydrology of the Little Ruaha River which is a major catchment of the Ihemi Cluster in the Southern Agricultural Growth Corridor of Tanzania (SA-GCOT) has been studied. The study focused on the hydrological assessment through analysis of the available data and developing a model that could be used for assessing impacts of environmental change. Pressures on land and water resources in the watershed are increasing mainly as a result of human activities, and understanding the hydrological regime is deemed necessary. In this study, modeling was conducted using the Soil and Water Assessment Tool (SWAT) in which meteorological and streamflow data were used in the simulation, calibration and evaluation. Calibration and evaluation was done at three gauging stations and the results were deemed plausible with NSE ranging between 0.64 and 0.80 for the two stages. The simulated flows were used for gap filling the missing data and generation of complete daily time series of streamflow at three gauging stations of Makalala, Ihimbu and Mawande. Results of statistical trends and flow duration curves, revealed decline in magnitudes of seasonal and annual flows indicating that streamflows are changing with time and may have implications on envisioned development and the water dependent ecosystems.

Tree Species Diversity and Edaphic Factors Associated with Different Land Uses in Tropical Forest Ecosystems, Tanzania

It has been reported that changes to miombo woodland ecosystems through conversion to other land uses alter tree species diversity and soil properties. The aim was to assess whether the Important Value Index (IVI), Shannon- Wiener diversity index (H'), and soil chemical properties differ between land uses in the Kibutuka miombo woodland ecosystem. IVI and H' were used to indicate tree species dominance and diversity. Statistical analyses were performed in R software. IVI of Brachystegia was significantly (p Combretum, Milletia, and Diplorhynchus had significantly (p p p p < 0.05) higher in intact forests than in the degraded forest. Degradation seen at a landscape scale for vegetation parameters, but not for soil parameters, indicates that the land use change taking place in the Kibutuka miombo woodland ecosystem is recent and the degradation seen in vegetation is still not reflected in the soil properties.

Evaluation for the Performance of the CORDEX Regional Climate Models in Simulating Rainfall Characteristics over Mbarali River Catchment in the Rufiji Basin, Tanzania

This study aims to evaluate the performance of the individual Regional Climate Models (RCMs) used in Coordinated Regional Climate Downscaling Experiment (CORDEX) and the ensemble average of the four RCMs to feign the characteristics of the rainfall pattern for the Mbarali River catchment in Rufiji Basin for the period of 1979 to 2005. Statistical analysis for model performance such as Root mean square error, Mean error, Pearson correlation coefficient, Mean, Median, standard deviation and trend analysis are used. In addition to the statistical measure of model performance, the models are tested on their ability to capture the observed annual cycles and interannual variability of rainfall. Results indicated that the RCMs from the CORDEX indicated a better performance to reproduce the rainfall characteristics over Mbarali River catchment in Rufiji Basin. They reproduced fairly the Era Interim annual cycle and inter-annual variability of rainfall. The ensemble average performed better than individual models in representing rainfall over Mbarali River catchment in Rufiji Basin. These suggest that rainfall simulation from the ensemble average will be used for the assessment of the hydrological impact studies over Mbarali River catchment in Rufiji Basin.

Impact of Land Use and Land Cover Changes on Surface Runoff and Sediment Yield in the Little Ruaha River Catchment

Little Ruaha River catchment (6370 Km2) in the Southern Agricultural Growth Corridor of Tanzania (SAGCOT), is one of the country’s most significant waterways due to its ecological composition and economic value. Regardless of its ecological and economical value, the regional hydrologic condition has been tremendously affected due to land uses alteration, influenced by different socio-economic factors. This study aimed to understand the associated impacts of the present Land Use Land Cover (LULC) change on the surface runoff and sediment yield in the Little Ruaha River Catchment. Hydrological modelling using Soil and Water Assessment Tool (SWAT Model) was done to quantify the impact of land use and land cover dynamics on catchment water balance and sediment loads. The calibration and validation of the SWAT model were performed using sequential uncertainty fitting (SUFI-2). The results showed that, for the given LULC change, the average annual surface runoff increased by 2.78 mm while average annual total sediment loading increased by 3.56 t/ha, the average annual base flow decreased by 2.68 mm, ground water shallow aquifer recharge decreased from 2.97 mm and a slight decrease in average annual ground water deep aquifer recharge by 0.14 mm. The model predicts that in the future, there will be a further increase in both surface runoff and sediment load. Such changes, increased runoff generation and sediment yield with decreased base flow have implications on the sustenance flow regimes particularly the observed reduced dry season river flow of the Little Ruaha River, which in turn cause adverse impacts to the biotic component of the ecosystem, reduced water storage and energy production at Mtera Hydroelectrical dam also increasing the chances of flooding at some times of the year. The study recommends land use planning at the village level, and conservation agricultural practices to ameliorate the current situation. Developing multidisciplinary approaches for integrated catchment management is the key to the sustainability of Little Ruaha River catchment.

Assessing the Impacts of Land Use and Land Cover Changes on Hydrology of the Mbarali River Sub-Catchment. The Case of Upper Great Ruaha Sub-Basin, Tanzania

Intensification of agricultural land use and population growth from 1990-2017 has caused changes in land cover and land use of the Mbarali River sub-catchment which is located in the Upper Great Ruaha Sub basin, Tanzania. This has affected the magnitude of the surface runoff, total water yield and the groundwater flow. This study assesses the impacts of the land cover and land use changes on the stream flows and hydrological water balance components (surface runoff, water yield, percolation and actual evapotranspiration). The land use and land cover (LULC) maps for three window period snapshots, 1990, 2006 and 2017 were created from Landsat TM and OLI_TIRS with the help of QGIS version 2.6. Supervised classification was used to generate LULC maps using the Maximum Likelihood Algorithm and Kappa statistics for assessment of accuracy. SWAT was set up and run to simulate stream flows and hydrological water balance components. The assessment of the impacts of land use and land cover changes on stream flows and hydrological water balance component was performed by comparing hydrological parameters simulated by SWAT using land use scenarios of 2006 and 2017 against the baseline land use scenario of 1990. Accuracy of LULC classification was good with Kappa statistics ranging between 0.9 and 0.99. There was a drastic increase in areal coverage of cultivated land, for periods 1990-2006 (5.84%) and 2006-2017 (12.05%) compared to other LULC. During 2006 and 2017 surface runoff increased by 4% and 9% respectively;however, water yield increased by only 0.5% compared to 1990 baseline period. This was attributed to increased proportion of cultivated land in the sub-catchment which has a high curve number (59.60) that indicates a higher runoff response and low infiltration rate.

Analysis of Land-Cover Changes and Anthropogenic Activities in Itigi Thicket, Tanzania

Assessing land cover changes from the 1991 to 2011 for Itigi thicket is imperative for determining changes between land cover types and understanding anthropogenic impact during this period. Remote sensing (RS) data, Geographic Information System (GIS) techniques and forest inventory data were used. ILWIS 3.3 Academic software was used to analyze the satellite imageries to determine the land use, land cover change;while data on anthropogenic activities were analysed in MS Excel software. The results showed that between 1991/2000 and 2000/2011, the areas of thicket declined by 6.23% while non-thicket areas increased by 3.92%. The decline in thicket areas was attributed to increase in anthropogenic activities such as wood extraction, clearing for agriculture, livestock grazing and fires. The study highlights the importance of integrating remote sensing and forest inventory in understanding the thicket resources dynamics and generating information that could be used to overcome the Itigi thicket problems for the sustainability of this unique vegetation.

Forms and Drivers of Conflicts between Farmers and Pastoralists in Kilosa and Kiteto Districts,Tanzania

Farmer-pastoralist conflicts represent a significant challenge for rural communities and the Tanzanian government.The study objectives were to(i)determine existing forms of conflicts and(ii)identify drivers underlying resource use conflicts.The manuscript is based on a study that adopted a cross-sectional research design whereby data were collected from 373 randomly selected respondents from Kilosa and Kiteto districts,Tanzania,while primary data were collected through interviews,observations and focus group discussions,secondary data were gathered from government reports and newspapers.Quantitative data were analysed using the Statistical Package for the Social Science(SPSS)version 20.0.Descriptive statistical analysis was carried out for quantitative data.Factor analysis was used to extract component factors on drivers and forms of conflicts,whereas content analysis was used to analyse the qualitative data.Generally,study results show that there were three main forms of conflict namely farmers versus pastoralists over village boundaries;farmers versus pastoralists over livestock routes and farmers versus farmers over the land.In addition,four main drivers underlying resource use conflicts were identified namely crop damage by livestock;inefficiency of government officials in taking action to diffuse conflicts;excessively large herds of cattle and corruption.It is therefore recommended that pastoralists should be provided with essential services such as water in order to minimize movement of their livestock herds from their designated villages to other areas in search of water.This would,in the long run,minimise crop damage which has been a major source of conflict.In addition,proper land use planning is recommended to minimize resource use conflicts.

The global Landsat imagery database for the FAO FRA remote sensing survey

To collect and provide periodically updated information on global forest resources,their management and use,the United Nations Food and Agriculture Organization(FAO)has been coordinating global forest resources assessments(FRA)every 5
10 years since 1946.To complement the FRA national-based statistics and to provide an independent assessment of forest cover and change,a global remote sensing survey(RSS)has been organized as part of FAO FRA 2010.In support of the FAO RSS,an image data set appropriate for global analysis of forest extent and change has been produced.Landsat data from the Global Land Survey 1990
2005 were systematically sampled at each longitude and latitude intersection for all points on land.To provide a consistent data source,an operational algorithm for Landsat data pre-processing,normalization,and cloud detection was created and implemented.In this paper,we present an overview of the data processing,characteristics,and validation of the FRA RSS Landsat dataset.The FRA RSS Landsat dataset was evaluated to assess overall quality and quantify potential limitations.