Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1989. / Includes bibliographical references. / Microfiche. / xiii, 145 leaves, bound ill. (some col.) 29 cm

Thesis (M.S. - Agricultural Economics)--University of Arizona, 1985. / Includes bibliographical references (leaves 95-97).

No description available.

Thesis (M.S. - Soils, Water and Engineering)--University of Arizona, 1985. / Bibliography; leaves 70-72.

A mathematical model for personal computers was prepared as a planning tool for development of micro catchment water harvesting systems. It computes runoff from natural or treated catchments, using estimated or actual parameters. The model also computes the water balance of the soil zone in the cultivated area and the water balance of the reservoir system which serves it. The model was calibrated with hydrolologic data and site characteristics for a location near Tucson, Arizona. Its prediction of cotton and grain sorghum yields was comparable to that of Morin (1977). An attempt was made to use weekly or monthly rainfall data for areas where daily data are unavailable. Lack of direct rainfall and runoff durations and infiltration characteristics made this attempt unsuccessful. This option cannot be used with the model in its current form.

A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements of the degree of Doctor of Philosophy. Johannesburg, February 2017 / Rainwater harvesting is used as a way of improving crop yields in rain fed agriculture by capturing excess rainfall and storing it in-situ or in reservoirs for use during dry spells. Contour ridges are one of the many rainwater harvesting technologies that are used although little is known about their effectiveness. Contour ridges harvest runoff generated in the cropped field upstream of the ridges. The traditional contour ridge type in Zimbabwe was introduced by the government in the 1950s to control soil erosion through safely draining away runoff from cropped fields and is commonly referred to as graded contour (GC) ridges. In the 1990s the country experienced severe and more frequent droughts leading stakeholders to experiment on contour ridges that retain the runoff instead of draining it away which are known as dead level contour (DLC) ridges. There was therefore the need to find out if there are benefits derived from this change and assess conditions under which benefits would be experienced. Previous studies have shown that rainwater harvested by contour ridges can improve water availability in downstream fields. However these studies did not investigate the conditions under which such benefits are realised. In addition no attempt to model water harvesting by contour ridges have been made in Zimbabwe while the contour ridges are widely being used for soil and water conservation. This research investigated the effect of contour ridges by comparing soil moisture between plots with DLC and GC ridges using plots with no contours as a control. Experimental work was carried out in Zhulube, in Matebeleland South Province of Zimbabwe. Matebeleland South Province falls within the semi-arid area in which rainfall is characterised by mid-season dry spells leading to frequent crop failure. In addition, the area often receives high rainfall intensities leading to soil erosion and sedimentation of rivers. DLC and GC ridges were constructed in farmers’ fields where maize crops were planted. Soil moisture measurements were done using a micro gopher soil moisture profiler while runoff plots were used to measure runoff generation. A fuzzy model was developed using data from this experiment and a previous study in Masvingo Province of Zimbabwe to simulate runoff generation at field scale while a process based water balance model was also developed to simulate soil moisture changes within the root zone of the cropped area. The results from this study indicate that DLC are effective in clay and loamy soils where runoff generation is significant and not in sandy soils due to insignificant generation of runoff under the rainfall regimes of semi-arid areas. Fuzzy logic was found to be a useful method of incorporating uncertainty in modelling runoff at field scale. A mass water balance model developed on process based principles was able to model soil moisture in the root zone reasonably well (NSE =0.55 to 0.66 and PBIAS=-1.3% to 6.1%) and could help to predict the water dynamics in contour ridged areas as would be required in determining the suitable dimensions and spacing of contour ridges. Further research is required to improve the fuzzy component of the model for estimation of runoff when more data becomes available. In addition experiments to validate methods of estimating macro pore fluxes and lateral transfer of water from the contour ridge channel to the downslope field are also recommended. The model structure can be improved by adopting the representative elementary watershed approaches to include momentum and energy balances in addition to mass balance that was used in this study. / MT2017

Dysfunctional rangelands lose nutrients and material faster than they capture or create them. The objective of this study was to determine the effectiveness of contour furrows, drill seeding, and aeration treatments in capturing overland flow, concentrating resources, and establishing perennial bunch grasses to convert dysfunctional semiarid rangeland to a functional rangeland. The site, located on the Edwards Plateau in west Texas, USA, had bare, structurally crusted soils with sparse short-grasses (Scleropogon brevifolius). The site had a low infiltration rate contributing to excess overland flow and loss of nutrients, organic matter, and soil. Contour furrows were installed with varying intra-furrow distances (0.6 to 61 m) and then broadcast seeded to determine if furrow spacing would produce a vegetative response. Portions of the intra-furrow areas were aerated and drill seeded. All seed mixes contained warm season, perennial bunch grasses (Bouteloua curtipendula, Leptochloa dubia, and Setaria leucopila). Soil beneath furrows had greater soil water content (p-value < 0.05) than intra-furrow areas. Furrow plots had greater density of seeded grasses and total vegetation (19 individuals m-2 and 191 individuals m-2, respectively) than intra-furrow plots (0 individuals m-2 and 89 individuals m-2, respectively). This study supports other findings that suggest 1.5 m to 1.8 m is optimum intra-furrow spacing. Vegetative responses to drill seeding and aeration treatments were insignificant. Observations suggest that contour furrows are effective at establishment and support of perennial vegetation by capturing and retaining water that otherwise would be lost to runoff from untreated soil.

Dysfunctional rangelands lose nutrients and material faster than they capture or create them. The objective of this study was to determine the effectiveness of contour furrows, drill seeding, and aeration treatments in capturing overland flow, concentrating resources, and establishing perennial bunch grasses to convert dysfunctional semiarid rangeland to a functional rangeland. The site, located on the Edwards Plateau in west Texas, USA, had bare, structurally crusted soils with sparse short-grasses (Scleropogon brevifolius). The site had a low infiltration rate contributing to excess overland flow and loss of nutrients, organic matter, and soil. Contour furrows were installed with varying intra-furrow distances (0.6 to 61 m) and then broadcast seeded to determine if furrow spacing would produce a vegetative response. Portions of the intra-furrow areas were aerated and drill seeded. All seed mixes contained warm season, perennial bunch grasses (Bouteloua curtipendula, Leptochloa dubia, and Setaria leucopila). Soil beneath furrows had greater soil water content (p-value < 0.05) than intra-furrow areas. Furrow plots had greater density of seeded grasses and total vegetation (19 individuals m-2 and 191 individuals m-2, respectively) than intra-furrow plots (0 individuals m-2 and 89 individuals m-2, respectively). This study supports other findings that suggest 1.5 m to 1.8 m is optimum intra-furrow spacing. Vegetative responses to drill seeding and aeration treatments were insignificant. Observations suggest that contour furrows are effective at establishment and support of perennial vegetation by capturing and retaining water that otherwise would be lost to runoff from untreated soil.

This report gives an overview on issues surrounding sustainable water management practices, specifically, rainwater harvesting (RWH), for low income households in South Africa. The agenda for sustainable development in South Africa has over time, downplayed the importance of Rainwater Harvesting. However, the South African Region is already a water scarce area, experiencing environmental and other threats to its limited water resources such as rapidly increasing demand for water from a growing population and economic sectors. A purely qualitative research method was used to conduct this Research Report which demonstrated that Rainwater Harvesting across the world can bring immense socio-economic and environmental benefits such as increased food security, improved sanitation and quality of the natural environment. A key question of this Research Report was to establish whether Rainwater Harvesting could be feasible for use in Low-income households in South Africa. This research revealed that the DoH and DWAF can constitute projects for Rainwater Harvesting for Low-income households in their programmes.

<p>Rainwater harvesting techniques are ancient practices that have been used for many years by different countries and civilizations. Runoff water harvesting is a promising technique to collect water and store it effectively in surrounding plant or crop areas. With global warming and climate change, water availability and accessibility are becoming even more critical, particularly in arid and semi-arid areas of the world. Annual rainfall is either scarce or insufficient to support farming practices in many areas. Thus, it is necessary to capture, store, and utilize water when it is sufficient for the growing season of different crops. In this sense, it is also important to evaluate differences in watersheds in terms of determining where the water flows (runoff areas) and where it can be collected for in situ use (run on areas). Based on land use, surface types, land cover, and soil group parameters, the amount of water changes within a watershed so it is crucial to determine and combine those factors. The aim of this study is to develop methodologies for determining the runoff harvesting potential of watersheds in arid and semi-arid areas. Specifically, to: 1) Identify potential areas for in-situ runoff harvesting (IRH)within watersheds; and 2) Estimate surface runoff volumes in areas as identified. The pilot study area for this study is Winters Wash Watershed, which is a sub-watershed of Centennial Wash located in Arizona (HUC number: 15070104). This watershed serves as a proxy for arid and semi-arid areas and was selected because it has sufficient data for the planned analysis. Based on the analysis, <a>17,615 ha (25% of the watershed area) were classified as being suitable or highly suitable as runoff sources, while 14,092 ha (20% of the watershed area) were better suited as run on collection areas. Total collectible runoff was determined on an average annual basis.</a> Finally, recommendations on suitable water harvesting techniques were made based on land use, soil, surface structure, and slope in the watershed. The results will provide a methodology for the decision-making process for identifying both run on and runoff areas and examples of real practices that could be used in places that are arid and semi-arid. </p>