Department of Engineering Sciences and Technology

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Assessment of environmental degradation in Nakambala Mazabuka Zambia
(Sokoine University of Agriculture, 1996) Chinjila, Mellon Halubanje
An environmental degradation assessment was carried out in Nakambala Estate, Mazabuka Zambia in October 1994 to June 1995 . The objectives of the study were: impact change, of the natural sugar plantation vegetation between 1970 and 1993 ; (b) and (a) on demographic resource degradation expansion land to assess the to assess the soil physical and chemical status in cultivated and abandoned areas; and (c) to compare current soil physical and chemical status of the study area with the status when the sugar plantation was being established. Sequential aerial photography was used in assessing sugar plantation expansion and its impact on natural vegetation and land resource degradation. The impact of the sugar plantation expansion on demographic changes and energy needs (fuelwood) was also assessed. A field soil survey was carried out to assess soil condition in terms of general fertility and selected land qualities and characteristics matched with the requirements of irrigated sugarcane using the FAO (1983) land suitability framework. Soil carried out by using indices. degradation assessment wasiii The results of the study were; the sugar plantation expanded by 7 035 ha between 1970 and 1991; human population increased by 4 929 (at 4% per annum) and projected to reach 22 127 by the year 2 000. to sugar Natural vegetation was reduced by 25 % due plantation expansion aggravating the fuelwood deficit situation (5 447 m3/year in 1970 and 4 906 m3/year in 1991) . There was no visible evidence of soil erosion although waterlogging was the prevalent form of land degradation in all the mapping units. The soils are generally eutric (base saturation > 50%) with slight acidic to neutral reaction in cultivated fields (in mapping units; 2W, 10, 11 and 12) to slightly alkaline reaction in areas with abandoned fields (soil mapping unit 13). High soil bulk densities occur in soil mapping unit 2W due to compaction by heavy machinery and due to inherent nature of the soils in mapping units 10, 11, 12 and 13 (heavy clays). Oxygen inavailability (due to poor drainage), physical degradation and poor rooting conditions (due to shallow effective soil depth) are the most limiting conditions for sugarcane changes in chemical status growing. Over time, noticeable (sodication) was low in all the mapping units except in unit 10 where sodication development was noticed. Adverse soil physical changes (crusting and surface sealing) occurred in soil mapping units 11, 13. 12 andiv To stem environmental deforestation, degradation in the form of energy utilization from fuelwood should be reduced by electrifying township housing units. The continued use of vetiva grass for drain protection is advised. Alternative land uses in soil mapping units 11, 12 and 13 and complete abandonment of monocropping practices in these soils is strongly recommended.
Digital processing of landsat thematic mapper satellite data for land cover classification using statistical methods for accuracy assessment: a case study of Ngerengere watershed
(Sokoine University of Agriculture, 1998) Mahuha, Fares Enock
This study involved primarily digital image processing and interpretation land for classification . cover Part of Ngerengere watershed covering about 300 km2 was taken as a case study Land cover which relates to the type of feature present on the surface of the Earth of the study area was elaborated. The procedures involved were reconnaissance survey to acquire 'a priori' knowledge about the u n s u pe r v i s e d area, classi f icat ion, field work classification, for rectification and restoration, ground supervised truthing, image ultimately producing and a land cover map of Ngerengere watershed. ERDAS 7.5 was the remote sensing (RS) software applied. The elaborated accuracy, land using cover map statistical was assessed packages. foric.s Overall classification accuracy (OCA) was about 70% which was below the recommended minimum level of interpretation accuracy value of 85%. It was however, revealed that the low OCA was substantially attributed by low producer's accuracy for the class of built-up areas which was only 22%. Although the produced land cover map had relatively low OCA, it had agood correlation with the present land use and vegetation. Further statistical analysis, by use of KHAT (K) statistics gave a value of 0.65 which is above 0.5 and approaches 1.0, hence acceptance of the land cover map produced from thatiii classification as primary data for land use planning. It percentage of also indicated extent the which to correct values of an error matrix used are due to true agreement and not by chance agreement. Chi-square (X2)distribution to test the goodness of fit of the land cover map elaborated, concluded absence of significant difference between the obtained and recommended OCA at significance level reject of and hence absence of enough evidence to 0.01, the classification for various applications like proposal for land use planning. In order to come up with a sustainable land use planning of the area, category other data are required. needed its own ancillary Every land cover data which are site specific to come up with. a proposal or alternatives for land use planning of an area. For instance, agricultural lands and rangelands classes needed much more ancillary data due to their spectral similarity and inseparability characteristics revealed during this study. Finally it is recommended for continuation of the study so as to come up with a sustainable land use planning of an area because thereis a problem already and timely intervention is imperative operation for the betterment of future generation.
Assesssment of the Perfomance of sun drying of maize grains on perforated surfaces
(1998) Silayo, V.C.K.; Kajuna, S.T.A.R.; Omari, B.
Sun drying of maize grains on different mesh sizes ofperjorated trays using different heights from the ground was investigated. The mesh sizes used were 1.5 mm and 3 mm at the elevations of 30, 60 and 90 cm. The results show that both mesh size and height from the ground affect the drying rate and seed viability. The combination of90 cm elevation and 3mm mesh size gave the highest drying rates and lowest seed viability loss.
Relationship between the Angle of Repose and Angle of Internal Friction for Agricultural Granular Materials
(1998) Kajuna, S.T.A.R.; Rugenga, E.
The angles of repose and internal friction are important parameters which determine the flow characteristics of agricultural granular materials, such as flour, maize, beans, wheat, sorghum and rice. The angles have a big influence on the design offlow and storage structures of agricultural materials such as hoppers, silos, bunkers and bins because they determine whether the flow will be smooth or not, and whether the bursting forces in relation to vertical forces will be great or not. An apparatus for determination of the angle of repose was specifically designed for the purpose. The a'ngles of repose for three different grains, namely maize, sorghulll and rice at four moisture content levels, namely 10, 15, 20 and 25%wb were determined using the designed apparatus. A tri-axial compression machine was used to determine the angles of internal friction for the same grains and same moisture contents. The data obtained were fed into SAS statistical software for step-wise regression analysis. A model of the form r = 22.35 + 0.013<1> 2; + 0.019[MC] 2 where r = the angle of repose, 1 = angle of intemlilfriction and MC = percent moisture content on wet basis was established, and used to predict the angleofreposefor the tested grains ~ith high accuracy (R2 = 0.97). It was concluded that the angle of repose was consistently higher than the angle of internal friction for all the granular materials tested, and the angle of internal friction was highest for maize, followed by rice and finally sorghum.
Review of rainwater harvesting techniques and evidence for their use in semi-arid Tanzania
(1999) Gowing, J.W.; Mahoo, H.F.; Mzirai, O.B.; Hatibu, N.
Raillwater h.{pvesting (RWH) ,shuuld"be 'regarded as a continuum of techniques thill' link in-situ soil-wate!: conservation at on~'exi;-'ellle to co'nventiona!irrigation {it the ·other. bHitu KWH, comprises i~ group of techniques for preventing runoff and promoting infiltration: Mic/'()-catc~mellt RWH comprises'a group'oftechniques/or collecting overlandfZow;(sheetor rill) from a catchment area and delivering it to a cropped.area in order to supplement the inadequate direc·t':air!faZ{ The transfer nomllllly occurs ·over a reJativelyshOit distance entirely withirt the land-holding of an individual farmer and the system is therefore sometimes known as 'an "illtemai cauhment" .. Macro-catchment RWH comprises a group' of techniques in which natural runoff is collected Fum a relatively large area .and. tr(1nsferred over.a longer distance. Examples of each pf these categories of RWH exist' ill p'a,t's 0/ Ta,';iania, but their potential is }eirgely neglected, by research and extension"seivices alzd they are illlder-exploited. The pUipose of this paper was to 'assess the extent to which thediflerent rainwater harvesting systeniS, are used in Tanzania. The findings show that there is a widespread practice of rainwater harvesting in Tanzania. Rainwater hmvestillg with storage of wate!' for livestock has received govemment SUppOit in the past . . However, rruzny storage reselvoir~ have been destroyed by siltation. On the other hand rainwater hmvesting for crop production has llOt received an adequate SUppOit from research and extension services. Therefore, although farmers are practiciizg rainwaterhmvesting, they are faced with sh01tage of appropriate technolo giesand know
Technical Note on Performance of Macro-Catchment Rainwater Harvesting for Maize Production: Preliminary Results
(1999) Kajiru, G.J.; Hatibu, N.; Bakari, A.M.; Kishebuka, S. R.; Young, M. D. B.
Macro-catchment raiilwater harvesting (RWH) describes those techniques witll much larger Catchment Areas (CAs) (generally > > Iha) which generally do not fall witllin a farmer's land. The CAs and Cropped basins (CBs) will often be very different in character and tlle transfer d.istance may be in tile range of a few hundred metres to several kilometres'- Although runotf efficiency is relatively lower tllan thy. 'microcatchment systems, runoff volumes will still be large because of tlle size of tlle CA. If the transfer distance is very large, it is also possible for tlle CA to receive rain and produce runoff for a CB which has received no rain. Macro-catchment RWH systems include: hillside systems such as tlle "ma jaluba" system of tlle Lake Zone of Tanzania (Meertens et aZ" 1999) where, water is ~hannelled intp bunded rice padis by small channekconstructed across ,tlle slope on grazing land; stream-bed systems which spread water tlowing in ephemeral streams using permeable stone dams or earth b~nds (van Dijk and Ahmed, 1993); and stt-eam diversion systems which chamlel water , trbm ephemeral streams into water-spreading s&uctures such a~ tlle "Caag" system of Somalik (Reij, 1991) The mairi problems with these : s~stems are, in controlling tlle sometimes very high volumes of runoff and preventing erosion. I The risk of too' much water washing away tiblds is a major problem in Western Pare I - Lowlands (WPLL).
Performance of maize under micro-catchment rainwater. harvesting in western Pare lowlands and Morogoro, Tanzania
(1999) Hatibu, N.; Gowing, l.W.; Mzirai, O.B.; Mahoo, H.P.
Micro-catchment Rainwater Harv.esting. (RWH) has been defined as a method of collecting run-off from a Catchment Area (CA) over short distances not exceeding 100 m and supplying it to an adjacent Cultivated Basin (CB). It is a system that is designed to concentrate rainwater so as to utilize it more effe"ctively in areas- where. the seasonal. rainfall amounts are frequently lower than crop water requirements. The Catchment to Basin Area Ratio (CBAR) is an important parameter in the design of micro-catchment systems. It usually varies between 1:1 and 10:1. However, methodsfor deciding the optimumle·ve! of CBAR for differef!t farming systems are not available. The purpose of the experiments reported here was to evaluate the CBARfor maize production in semiarid areas of Tanzania. The experiments were run between 1992 and 1995. in semi-arid areas of Morogoro and Mwanga Districts of Tanzania, to assess the peiformance of maize grown in microcatchment systems with CBAR varying from 0:1 to 4:1. Maize var. TMVI was grown in Mwanga District while maize-var. Staha was used as a test crop in Morogoro District. Grain was harvested in five out of six experimental seasons in Mwanga (Masika 1993, 1994 and 1995 and Vuli 199411995 and 199511996). In Morogoro, grain harvest was obtained only in two seasons (Masika 1993 and 1994) out offour. The results showed that micro-catchment RWH farming is feasible during Vuli. The yield benefits due to RWH were found to be 120 - 152· % and significant at P = 0.05. The benefits during Masika were found to be very low at only 12 - 17 % and not significant at P = 0.05.
Soil nitrogen dynamics and relationships with maize yields in a gliricidia–maize intercrop in Malawi
(Kluwer Academic Publishers, 1999-04) Ikerra, Susan T.; Maghembe, Jumanne A.; Smithson, Paul C.; Buresh, Roland J.
Many soils of southern Africa are severely N deficient, but inorganic fertilizers are unaffordable for most sub- sistence farmers. Rotations and intercrops of legumes with crops may alleviate N deficiency through biological N 2 fixation and redistribution of subsoil N to the surface. We monitored soil inorganic N dynamics for two seasons in a gliricidia [Gliricidia sepium (Jacq.) Walp.] – maize (Zea mays L.) intercrop in the unimodal rainfall area of southern Malawi. One maize crop per year was grown with or without interplanted gliricidia, in factorial combination with three rates of N (0, 24 or 48 kg N ha −1 ). Application of gliricidia prunings increased (p < 0.001) topsoil (0 to 20 cm) inorganic N at the end of the dry season and during the early rains. Differences between plus and minus gliricidia treatments were less when total inorganic N to 1-m depth was summed. A greater proportion of the total inorganic N to 1-m depth occurred in the topsoil (0 to 20 cm) when gliricidia was present, suggesting that redistribution of subsoil N to the surface accounted for part of the N increase by gliricidia. Gliricidia lowered (p < 0.05) subsoil water content during drier periods. Gliricidia plots accumulated more (p < 0.01) ammonium-N during the dry season. Nitrate-N remained constant during the dry season but rose rapidly in gliricidia plots after the onset of rains. A 2-factor model including preseason inorganic N and anaerobic N mineralization potential accounted for 84% of the variability in maize yields for the two seasons’ data combined. The combination of preseason inorganic N and potential N mineralization appears to provide a good estimate of N supply to maize in systems receiving both organic and inorganic sources of N.
Modelling and measurement of soil moisture content based on a remote sensing method for applications in Semi-arid tropics.
(University of Bonn, 1999-06-18) Salim, Baanda A.
Soil moisture plays a very crucial role in land surface processes It should therefore be monitored with the same accuracy and frequency as other important environmental variables Two approaches are used for estimation of soil moisture content, namely, modelling and measurement, either in-situ or remote. Integration of modelling and measurements may provide the best solution towards estimation of soil moisture content The utility of ground-based thermal infrared remote sensing method for the estimation of nearsurface soil water content was tested under tropical semi-arid agricultural conditions in Morogoro, Tanzania, East Africa Field experiments were conducted between January and August, 1997 at a bare soil site Regression relationships between the daily maximum surface soil temperature minus air temperature (TDMax) and weighted-average soil water contents to different depths in the soil profile were developed based on the measured data Better correlations were obtained for the top 0-5 and 0-15 cm layers of the soil, with coefficients of determination ofO 81 and 0.78, respectively Use of "Normalized TDMax" as well as cloudncsscover- correctcd "Normalized TDMax” (TDaMax) resulted in even better coefficients of determination (c g , 0 95 for the 5 cm depth) A physically based model of coupled flow of heat and water in the soil (SUAHEAT) was developed The SUAHEAT model was tested by comparing its simulated soil water contents and soil temperatures with those measured at the bare soil site Both qualitative as well as quantitative methods were used to evaluate the model performance, for the calibration and validation phases For the calibration phase, the average values of the mean absolute difference (MAD) of soil water content were 0.06, 0 05, 0 05, and 0.03 m7nP for the 5, 15, 30, and 45 cm depths, respectively The corresponding average values of the root mean square difference (RMSD) of soil water content were 0.07, 0 06. 0 05, and 0 03 m’/m’ for the same depths, respectively As for the validation phase, the average MAD values of soil water content were 0 09, 0.05, 0 08, and 0 17 nP/nP for the same depths, respectively. The corresponding average RMSD values for the same depths were 0 12. 0 08, 0 10, and 0 19 nP/nP, respectively The unusually large errors (at the 45 cm depth) during the validation phase could be attributed to the overestimation of soil water content values during very wet conditions arising from the calibration equation used. The performance of the model in the simulation of surface, near-surface, and profile soil temperatures was also both qualitatively and quantitatively evaluated In the calibration phase, the MAD values were 2 8, 1 1,0 5, and 0 3 °C for the 5, 15. 30, and 45 cm depths, respectively. The corresponding RMSD values for the same depths were 3 5, 1.3, 0.6, and 0.4 °C, respectively. For the validation phase, the MAD values for the same depths were 2.3, 1 2, 0 7, and 0.4 °C, respectively. The corresponding RMSD values for the same depths were 2.7, 1.4, 0.8, and 0.5 °C, respectively. Generally, the errors obtained with the use of the SUAHEAT model are comparable to values obtained by other researchers elsewhere using similar models. Integration of the model with remotely sensed surface soil water content and temperature data was effected through use of the initial profiles of soil water content and temperature. The initial profile data were derived from the regression relationships between TDMax and surface soil water content on the one hand, and between the surface and profile soil temperatures on the other, respectively. Model simulation results obtained using the remotely sensed initial conditions indicated that it is feasible to use remotely sensed data (one value of TDMax per day) to initialize the model Similarly, extrapolation of the remotely sensed near-surface (0-5 cm depth) soil water content to values at greater depths in the soil profile was shown to be feasible.
Validation of crop weather models for crop assessment arid yield prediction under Tanzania conditions
(2000) Kihupi, N.; Dihenga, B.O.; Ntella, P. M.
Information gatheringfor early warning and crop assessment in Tanzania is based on physical inspection of standing crop in sample jields. This process is subject to human error, inadequate and is also time consuming. Recent developments in computer simulation have paved the way for more efficient methods of analysing datafor purposes of early warning and crop assessment. Two such sch~mes based on soil water balance simulation, viz. IRSIS and CRPSM models were used in this study fo see how closeZv they could predict grain yieldsfor selected stations in Tanzania. Inputfor the models comprised of weather, crop and soil data collected from jive selected stations. Simulation results show that IRSIS model tends to over predict grain yields of maize, sorghum and wheat, a fact that could be attributed to the inadequacy of the model to accurately account for rainfall excess. On the other hand, the CRPSA1 model simulated results were not significantZv different (P>O. 05) from the actual grain yields ojmaize, sorghum,. wheat and beans. Although the agreement between actual and simulated yield data was good, it was observed that mean valuesfor predicted grain yields were consistently lower thanfor actual grain yields. This could be attributed to the use of approximate rather than location specific input parameters required by the CRPSM model. Locally calibrated input parameters in the CRPSM model could filrther improve the accuracy of the model and hence its ability to predict grain yields.
Major factors influencing the occurrence of landslides in the northern slopes of the Uluguru mountains, Tanzania
(2000) Kilasara, M.; Mtakwa, P. W.; Poesen, J.; Deckers, J. N.
Landslide mitigation largely depends on the understanding of the nature of the factors that have direct bearing on the occurrence oflandslides. Identification of these factors is of paramount importance in setting out appropriate and strategic landslides control measures. The present study focused on the identification of the major factors influencing the occurrence oflandslides in the Northern slopes of the Uluguru Mountains, Tanzania. The main objective was to establish relationship between spatial distribution of landslides and their causative factors. Such information would enable the planning of appropriate and strategic control measures. Aerial photographs, field survey and Geographic Information System (GIS) techniques were employed to identify the landslides features which occurred during EL NINO rains, spatial distribution and their corresponding factors. The results show that landslides dominate the geomorphic units with slope gradient ranging from 25% to over 80%. The most affected geomorphic units are in the order: debris slopes> incisions and V-shaped valleys > amphitheatres. Factors which cause theoccurrence of landslides are both soil and terrain related. The most important soil characteristics are presence of shallow soil solum with low bulk density and high macro porosity overlying a relatively less porous saprolite or hard bed rock. The terrain related factors include: undercutting of slopes by roads and pathways and presence of very steep concave side slopes. Water flow from roads and pathways and seepage from irrigation channels are precursors for the triggering oflandslides in the study area.
Effects on direct sun drying of maize grains on perforated and unperforated surface
(2000) Silayo, V.C.K.; Woods, J. L.
Sun drying ofmqize grains on unperforated and perforatedsurfaceswas conducted under simulated solar radiation intensity of afJout 800 Wlm: and in the field, where solar radiation intensity was variable. ,The drying depths employed were 10, 20, 30 and 40 mm under simulated solar radiation conditions and 20 and 40 mm in the field The response variables measured were weight loss at all depths and moisture content and temperature distributions in the 40-mm depth bed The results in terms of overall drying rates indicate that, at depths greater than 10 mm, the perforated surface was superior (P < 0.05) to the unperforated and at 40 mm th.e efJectwas about double that of the contro/. Changi,!gof dryingdepthfrom 10 to. either 20 or 30 mm on the perforated surface did not affoct the specific drying rates significantly (P < 0.05) 'except on 40/,;;n depth. On the unperforated surface the overall specific drying rates decreased significantly (P
Modelling the water balance of a small catchment: A case study of Muhu catchment in southern highlands of Tanzania
(Sokoine University of Agriculture, 2000) SHIBA, S1PHO SIMEON S. T.
I'he water balance ol'Muhu catchment located in the Southern Highlands of Tanzania in Iringa region was modelled by establishing the empirical relations that exist between storage parameters, rainfall parameters and runoff components. Storage parameters included soil moisture storage and interception. Rainfall parameters included rainfall amount, intensity, duration. throughfalL stemflow and evaporation. Runoff components included total runoff, direct runoff and base How. The catchment's physical and hydrological characteristics that affect these parameters were determined. 1 he assessment of hydrological and physical properties showed that the soils were predominantly sandy clay, having high organic matter content, with a moderately rapid hydraulic conductivity (Ks) of 4.2 cm/h and infiltration rale of 3.8 cm/ h. The bulk density was generally low with an average of 0.9 g/cnT for 0-15 cm depth: 1.1 Ig/cm5 for 15-30 cm depth and 1.30 g/cm’ for 30 - 45 cm depth. The catchment had a slope steepness of 35 % and a varying vegetal percentage cover of about 56 %. The 1997/98 waler year was exceptional with high rainfall (1934 mm) mainly due to the El-nino phenomenon. Sixty-seven percent of the rainfall received in the catchment penetrated the canopy to reach the forest floor as throughfalL On average 3.3 % of the rainfall reached the forest floor as stem flow' while 25.5% of the rainfall was intercepted by the canopy. ThroughfalL stemflow and interception were linearlyIll related to rainfall. Die regression coefficients of all the relationships were significantly different from zero al 1% level (fteO). With increasing percentage surface cover, interception increased while throughfall decreased. The storage capacity of the forest cover was estimated to be 0.7 mm.
Land suitability evaluation for the production of the major crops in the southwestern part of the Uluguru Mountains, Morogoro rural district, Tanzania
(Sokoine University of Agriculture, 2001) Kimaro, D. N.; Msanya, B. M.; Mwango, Sibaway, B.; Kimbi, Gerald, G.; Kileo, Emmanuel, P.
Land evaluation study was conducted on the southwestern slopes of the Uluguru Mountains in Morogoro Rural District, Tanzania to assess the potentials and constraints of the various land units for the production of low input rainfed cabbage, round potato and arabica coffee. The study area is located between latitudes 7 o 0000 and 7 o 1123.5S and longitudes 37 o 3000 and 37 o 3836.6E covering the villages of Kibaoni, Langali, Bunduki, Bumu, Kikeo, Luale, Mwarazi, Nyandira, Kibuko and Tchenzema. The areal extent is 419.64 km 2 (41,964 ha) with an average elevation ranging between 900 - 2700 m a.s.l. The mean annual rainfall in the study area ranges from 1065 mm to 2450 mm. The rainfall distribution pattern is monomodal with the rainy season starting from December to May. The peak rainfall occurs in April in most places of the study area. The high altitude areas receive more rainfall than the lower areas. In some areas rainfall distribution tends more to be bimodal with two peaks occurring in October and in April. There is considerable temperature variability in the study area with the mean monthly temperature ranging from 17.4 o C (July) to 22.4 o C (December). At high elevations temperatures are much cooler. The shortest reference length of growing period is 180 days while the longest is 270 days. The geology of the study area consists of a mixture of banded pyroxene granulites with occasional biotite-rich bands, foliated mica gneisses, hornblende gneisses and granulites and some iron-rich meta-anorthositic rocks, all belonging to the Usagaran system. In some places alluvial deposits and kaolinitic clays of Neogene age are found. The study area consists of strongly dissected mountains with very steep plateau and ridge slopes of about 30-60% and narrow valleys and incisions. Lukwangule plateau is the highest peak in the study area reaching an altitude of 2,623 m a.s.l. The Lukwangule plateau is only slightly dissected and the surface forms quite a mature relief. Two distinct drainage patterns exist in the study area. A sub-radial pattern which is related to the horse-shoe of high mountains from Mkumbaku through Lukwangule and Magari to Lupanga, which is currently represented by some of the larger rivers such as Mngazi, Mbakana and, in part, the Mgeta. A rectilinear pattern is exhibited where secondary streams and many main rivers show adjustment to geological structure and rock type. The pattern of the minor rivers follows the geological structure more closely and has resulted in river capture, reversed drainage and wind gaps. The edge of the meta-anorthosite is marked by the Mgeta, Mfunesi and Lukangazi river valleys for about two-thirds of its circumference, and this weakness is presumably the cause of the spiral course of the Mgeta River as it cuts back along the junction of rocks, capturing successively all the radial drainage from the north and west of the high level plateaux.
Investigation of laser and ultrasonic ranging sensors for measurements of citrus canopy volume
(American Society of Agricultural Engineers, 2002) Tumbo, S. D.; Salyani, M.; Whitney, J. D.; Wheaton, T. A.; Miller, W. M.
This study compared ultrasonic and laser measurements of citrus canopy volume with manual measurement methods. Fifteen trees with different canopy heights and volumes were used. Manual and ultrasonic measurements provided dimensions for computing the canopy volume whereas laser measurements gave information that could be used to compute a ‘laser canopy volume index.’ Ultrasonic and laser methods agreed with manual methods (R2 > 0.85, RMSE < 2.15 m3). Laser showed better prediction of canopy volume than the ultrasonic system because of the higher resolution. Ultrasonic or laser sensors can be used for automatic mapping and quantification of the canopy volumes of citrus trees.
Failure of the Mtera-Kidatu reservoir system in the Early 1990s
(SUA, 2003) Yawson, D.K.; Kachroo, R.K.; Kashaigili, J.J.
Four possible causes for the failure of the Mtera-Kidatu Reservoir System within the Rufiji River Basin in Tanzania in the early 1990s were investigated. These were sudden decrease in inflows, sudden increase in losses, sudden increase in hydropower generation, and unnecessary spills; or a combination of these, and it was found out that unaccounted for and unnecessary spillage was the main cause. This paper proposes that consideration of the flows that are generated within the intervening catchment (i.e. catchment between Mtera and Kidatu) and the operational policy that maximum power is produced at Kidatu most of the time must be the core in the management of the reservoir system. If this was the case in the past then the Mtera Reservoir should not have gone dry in the 1991-1994 period. The validity of this assertion was tested with the TALSIM 2.0 model and an efficiency of 95% was achieved, indicating a very good correlation with the investigative techniques employed in this study.
Water productivity indicators in great Ruaha river basin: analysis and implications for decision-making and allocating water
(SUA, 2003) Mdemu, M.; Lankford, B.; Kadigi, R.M.J.; Cour, J.; Kashaigili, J. J.
The assessment of benefits from water by applying the concepts of water productivity is gaining momentum for managing water resources in river basins. A number of institutions have been in the forefront of spearheading the concept. The attractiveness of the water productivity concept is partly due to its diversified nature in looking at benefits of water use, both intended and unintended in a particular system. The benefits may include area irrigated, number of families depending on a particular source of water, number of jobs created as a result of presence of water. This paper explores water productivity indicators and their implications for allocating water drawing the example from the Great Ruaha River Basin. In addition to the primary and secondary indicators of productivity, the paper develops the concept of tertiary indicators (labelled ‘specific hydrovalue’) to express the economic benefits gained per person per cubic metre of water used. The paper concludes that water productivity indicators (WPIs) can be used as a tool for analysing the tradeoffs and prioritising of water use and allocation in competing and non-competing water uses but that much more conceptual and computational analysis is required
Modelling the Mtera-Kidatu reservoir system to improve integrated water resources management
(Hydro Africa, 2003) Yawsona, D.K.; Kashaigili, J.J.; Kachroo, R.K.; Mtalo, F.W.
Failure of the Mtera-Kidatu Reservoir System within the Rufiji River Basin in Tanzania in the early 1990s is investigated by considering four possible causes (i.e. sudden decrease in inflows, sudden increase in losses, sudden increase in hydropower generation or unnecessary spills; or a combination of these) and it was found out that unaccounted spillage seems to be the main cause. Consequently, the system’s simulation model has been proposed in this paper that takes into consideration the flows that are generated in the intervening catchment (i.e. catchment between Mtera and Kidatu) with the operational policy that maximum power is produced at Kidatu most of the time because Kidatu has higher head for greater power generation than at Mtera. The paper shows that if this proposed model had been in place then the Mtera Reservoir should not have gone dry in the 1991-1994 period. The validity of the proposed model is tested with the TALSIM 2.0 Model and the regression analysis of the water levels at Mtera Reservoir produced by the models had an efficiency of 95%, indicating a very good correlation. The proposed model operates the reservoir system in an integrated manner by considering the flows into the Mtera Reservoir as well as accounting for the flows generated by the intervening catchment.
Rice production economics at the local and national levels: the case of Usangu plains in Tanzania
(International Water Management Institute (IWMI), 2003) Kadigi, Reuben M. J.
This report explores the production economics of paddy at the basin (Usangu), district (Mbarali), regional (Mbeya) and national (Tanzania) levels. The important features of the report are summarized in the document.
Mapping uses and competition for shared water resources: conflicts and values in Mkoji sub-catchment, Tanzania
(Loskopdam, South Africa, 2004) Hermans, Leon M.; Kadigi, Reuben M. J.; Mahoo, Henry F.; Halsema, Gerardo E. van
Conflicts over water are a common feature in closing basins and the difficulties in resolving them provide a serious barrier for the formulation of an effective IWRM strategy. Understanding the specifics of a conflict, including its dynamics and its evolution, provides an essential basis for subsequent efforts towards conflict resolution. Since conflicts are driven by interests and values of stakeholders, insight into the values underlying conflicts may further help the identification of promising ways to resolve them. Especially the latter is of crucial importance, as the identification of effective solutions to conflicts still remains more of an art than a craft. This paper discusses the use of two analytic frameworks that support a better understanding of local conflicts over water: conflict analysis and value- focused thinking. It illustrates the use of these frameworks to analyse local water conflicts in a closed sub-catchment in Tanzania. It shows how these frameworks support the identification of solutions that can help local stakeholders to “create value” in closing basins. On the basis of this illustrative analysis, the paper argues that these two frameworks deserve a wider use in the field of local water management.

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