In the gravimetric calibration method of water meters, the volume of water that has passed through the equipment under test (EUT) is generally collected into a tank and the quantity (mass) determined by weighing. The mass of water collected is then converted into a volume. This conversion of mass into volume requires knowledge of the water density, which can be estimated, measured directly or determined by other means. The error of measurement of the EUT is determined by comparing the volume recorded by the EUT and the volume collected in the tank. The density of water is, therefore, one of the major causes of measurement uncertainty in laboratory calibration of water meters using the gravimetric method. Water meter calibration facilities commonly use density formulations proposed by the International Standards Organisation (ISO) and the Organisation for International Legal Metrology (OIML). In Australia, additional guidance in water density determination is provided by the National Measurement Institute (NMI). In this study, testing was undertaken using ten positive displacement water meters arranged in series in the test rig to evaluate some of the common water density formulations used in Australia. The effect of these different formulations on the water meter error measurement was determined, as well as the effect on the measurement uncertainties. The results shows that the use of these different density formulations evaluated do not significantly affect the water meter error of measurement or the uncertainty of measurement. There was no apparent correlation between the water meter error and the meter position in the test rig. It was also determined that if the water density was adjusted only for temperature effects, a maximum of 0.05 and 0.15% drift in meter error and measurement uncertainty respectively, can be expected.

Climate change and variability are projected to alter the geographic suitability of lands for crop cultivation. In many developing countries, such as Kenya, information on the mean changes in climate is limited. Therefore, in this study, we model the current and future changes in areas suitable for rainfed maize production in the country using a maximum entropy (MaxENT) model. Maize is by far a major staple food crop in Kenya. We used maize occurrence location data and bioclimatic variables for two climatic scenarios-Representative Concentration Pathways (RCP) 4.5 and 8.5 from two general circulation models (HadGEM2-ES and CCSM4) for 2070. The study identified the annual mean temperature, annual precipitation and the mean temperature of the wettest quarter as the major variables that affect the distribution of maize. Simulation results indicate an average increase of unsuitable areas of between 1.9–3.9% and a decrease of moderately suitable areas of 14.6–17.5%. The change in the suitable areas is an increase of between 17–20% and in highly suitable areas of 9.6% under the climatic scenarios. The findings of this study are of utmost importance to the country as they present an opportunity for policy makers to develop appropriate adaptation and mitigation strategies required to sustain maize production under future climates

Ecohydrological changes in large rivers of the world result from a long history of human dimensions and climate. The increasing human population, intensified land use, and climate change have led to a decline in the most critical aspect of achieving sustainable development, namely, that of water resources. This study assessed recent hydromorphological characteristics of the tropical Tana River in Kenya using flow duration curve, and geospatial techniques to gain a better understanding of human impacts over the last two decades and their consequences for new development projects. The results show that all extremal peak, low, and mean discharges exhibited significant increasing trends over a period of 17 years. Dam construction represents a 13% reduction of the maximum discharge and a 30% decrease in low flows, while post-regulation hydrological changes indicated an increase of 56 and 40% of high flows and low flows respectively. Dominant flow was observed to be higher for the current decade than the previous decade, representing a rise of the dominant streamflow by 33%. The assessment of four morphologically active sites at the downstream reach showed channel adjustments which support the changes in the flow regimes observed. The channel width increased by 8.7 and 1.9% at two sites but decreased by 31.5 and 16.2% for the other two sites under study during the time period. The results underscore the contribution of other main human modifications, apart from regulation, such as increased water abstraction and inter basin transfer, up-stream land use and anthropogenic climate change to assess the ecohydrological status in this river basin. Such streamflow regime dynamics may have implications on water resource management, riverine environments, and development of new water projects.

Deforestation poses a threat to sustainability of forest ecosystem services and socio-economic development in many parts of Kenya. Understanding the trend and extent of forest cover changes and the underlying driving forces over time is pertinent for sustainable management of ecosystems. However, in many parts of the country, such information is still somewhat unknown due to limited data availability for multi-temporal analysis. This paper focuses on western Kenya, a major agricultural region of biodiversity and water catchments that are under threat from forest cover dynamics. The study analyses the status of the forests in the region with the aim of determining the areal extent of coverage, trends in forest cover, drivers of change and associated impacts of deforestation. To achieve these objectives, remote sensing techniques were used to undertake supervised classification on Landsat images of 1995, 2001, 2010 and 2017 with classification scheme of forest and non-forest land cover classes. The results of the study showed that the changes in forest cover varied over time and space. There was considerable net gain in forest areas by about 43% between the period 1995–2001, and thereafter, a continuous decrease ending in a 12.5% loss by 2017. Deforestation in the region is caused by a combination of complex factors that include population pressure, politics and failures in implementation of policy. This study determined the forest cover dynamics and driving forces across diversified sub-basins, an approach that had not been used by previous studies in the region. Thus, the findings will provide valuable information for decision making pertaining to integrated land use and catchment management in order to realize the enormous benefits of sustainable forest ecosystems. The information will not only be important to the study area, but equally applicable to similar tropical regions.

The hydraulic performance of large-diameter gated fluming, commonly used in furrow irrigation, was investigated using computational fluid dynamics (CFD). The continuity and the momentum equations governing the fluid in the system were solved numerically for a steady incompressible and turbulent flow using a realizable software model. The CFD results were compared with the laboratory measured results and those obtained using a hydraulic simulation model. The CFD results showed a good correlation with the measured data and those generated using the software. The velocity head in the pipeline had no influence on the magnitude of the outflows possibly due to the unique shape of the outlet. The pressure head recovery across the outlets was greater than the energy loss along the pipe; hence, the pressure and discharge increased towards the downstream end. The CFD approach was found to be an appropriate tool for detailed analysis of the hydraulic characteristics of gated irrigation pipelines.

The International Network of Irrigation Testing Laboratories (INITL) undertook a sprinkler intercomparison testing exercise to generate data for an objective comparison of the performances of the different facilities and identify opportunities for further improvements. Three impact sprinklers were tested in four laboratories in accordance with established standards. The plots of flow rate-pressure profiles were found to be consistent, and correlated to those obtained from previous studies. Although there were slight variations in the measured flow rate data, the mean flow rates at each pressure level were the same for the three sprinklers, and the shapes of the radial distribution profiles were similar. The deviations of reconstituted flow rates (from the measured) of at least two tests in each facility were found to exceed the recommended limit. The sprinkler software developed by INITL was found to have a good correlation with a related commercial software program.

The International Network of Irrigation Testing Laboratories (INITL) undertook a laboratory inter-comparison testing exercise of three sets of drippers in the period 2013 and 2014. The four testing facilities that participated in this exercise are based in following countries: Australia, Brazil, France and China. The objective of the testing programme was to compare results from different independent testing facilities to enable individual laboratories identify potential opportunities for improvement of their performances. This would also facilitate the INITL to make proposals for harmonisation of the testing methods. The maximum coefficient of variation, cᶹ, at the manufacturer's recommended operating pressure of 100 kPa, was found to be 3.76%, which was significantly smaller than the 7% recommended by ISO 9261 [5] as the maximum allowable variation of the flow rate of the test sample. The emitter exponent was determined to be approximately 0.5 which is consistent with results obtained from past studies. At the operating pressure of 100 kPa, it was found that although the average flow rates from the participating laboratories were similar, there was a difference in the dispersion of data. Datasets for the 4 Lh‾¹ dripper model fitted a normal distribution model, while on the other hand, some data sets for the 2 and 8 Lh‾¹ dripper models were not normally distributed. A higher dispersion of measurements can be interpreted as a higher instability of the testing conditions. The variance for the 2Lh‾¹ dripper model was found to be homogeneous, while non-homogeneous for the other two models. The latter implies that at least one of the laboratories presented an uncertainty of measurement significantly different from the others. The measurement uncertainty undertaken in this study demonstrated that there were opportunities to improve the measurement process. Recommendations and suggestions for harmonisation of test procedures and improvements in individual laboratories are also identified in this paper.

River channel dynamics are natural autogenic occurrences for fluvial rivers with influences from human modifications and climatic factors. Remote sensing and geographic information system tools and techniques, aerial photographs, and satellite imagery have been used to determine epochal channel erosion, accretion, and unchanged locations along Tana River, Kenya's longest river. Six reaches within a 142-km Saka-Mnazini stretch were studied by comparing sequential changes in the position of the channel in 1975–1986, 1986–2000, 2000–2017, and 1975–2017 epochs. Manual and automatic digital processing procedures and GIS tools were applied to visualize and quantify the reach-wise spatial and temporal morphological changes. The erosion and accretion channel changes over the study period were observed and quantified at all reaches. Meandering and switching off or abandoning the main active channel was also illustrated. The potential driving forces of morphological changes included varying hydrological regime, upstream land use practices, nature of channel gradient, and riparian vegetation occurrence changes. We found no clear evidence to link river regulation with the river channel dynamics. Results deliver the latest evidence on the dynamics of Tana River. This information is crucial for understanding river evolution characteristics and aid in planning and management at the lower reaches which has remained poorly understood. Use of remote sensing data in concert with GIS provides efficient and economical quantitative spatial and temporal analysis of river channel changes.

The aerial photographs, taken on the 6th of February 1975 at a scale 1: 50 000, were obtained from the Survey of Kenya and were used to generate my original data.

The catch can method is traditionally used for evaluating performance of drip systems. Two variations of this method are commonly applied in laboratory testing of drippers: the sequential and the simultaneous method. This study compared uniformity and measurement uncertainty of the two methods, with the overall aim of improving irrigation water management. The simultaneous method was found to have a lower coefficient of variation(Cν) and measurement uncertainty, indicating that it is more accurate than the sequential method. In all the tests, however, the Cν was determined to be <5%, which is acceptable as per the current reference standard.