Non-point source pollution processes and connectivity modelling in the Mkabela Catchment, South Africa.

Ph. D. University of KwaZulu-Natal, Pietermaritzburg 2015.In South Africa water resources and water quality issues are becoming increasingly important as the country manages its scarce water resources. The National Water Act of South Africa Act 36 (1998) stipulates that water resources must be shared in a sustainable fashion among humans, environment and economic land uses. Deterioration of water qualities in rivers are not only unique problems to South Africa. Indeed the degradation of water quality by nutrients originating from agriculture through excessive use of fertilizers (NO₃ and P) and erosion (sediments) is an international environmental concern. Rivers passing through agricultural areas experience high pollution levels from non-point sources resulting from these agricultural activities. Dealing with this issue is not straight forward because the agricultural contribution to diffuse pollution varies widely as a complex function of soil type, climate, topography, hydrological connectivity, land use and management. This creates widespread, intermittent, and poorly defined contaminant sources that degrade water quality in a way that makes their control difficult. In recognition of the accelerated degradation of water bodies from agricultural Non-Point Source (NPS) pollutants, watershed models have evolved from traditional hydrology models to more comprehensive water quality models. Diminished use or even loss of the water resource for other beneficial uses has resulted from over burdening of the receiving waters with waste fertilizers from agriculture. For example, many surface and groundwater bodies used as a water supply have lost their utility due to agricultural pollution. Upstream users of land do not feel the economic impact of their action on the downstream users who must use water from other sources because the water quality of their source was rendered unusable. Farmers respond to their economic realities, i.e. they want to make at least some profit or at least survive during harsh economic situations, both of which can be accomplished by increased crop yields. Without some intervention in the farmers’ economic reasoning, the potential water quality problems far downstream is not a part of the farmers’ decision making process with regards to how much fertilizers they will use on their land or how to dispose of their animal waste. The new ACRU-NPS (Agricultural Catchment Research Unit- Nitrogen, Phosphorous and Sediments) model was developed to try to address these challenges. The model was configured using a nested approach, which requires an effective description of all relevant components of the system and an understanding of the processes and feedbacks taking place within and between different scales and hydrological processes response zones. The concept of connectivity in the model was introduced to improve simulations. Connectivity defines the physical coupling of landforms (e.g. hillslope to channel) within a catchment where the passage of water from one part of the landscape to another is expected to generate a catchment runoff response that may carry along with it dissolved pollutants, sediments and any contaminants that they may carry through the drainage basin. The connectivity of the river (drainage) network in the Mkabela Catchment (near Wartburg, KwaZulu-Natal) was assessed on a sub-catchment basis and was linked to in-stream controls that included farm dams, wetlands and buffer zones where the fate and transport of dissolved N and P, sediment and associated adsorbed P were studied. A new method of calculating crop yield, different from that used in the SWAT (Soil and Water Assessment Tool) model, was developed and incorporated in the ACRU-NPS model. In the new method water and nitrogen stresses were used to limit crop growth on a daily time step. This enabled consequences of subsequent nutrient and sediment loads in streams to be studied. The major limitation to long-term use of SWAT in South Africa is the lack of long-term nutrient and suspended solids data for calibration and validation. This study utilized the new ACRU-NPS modelling approach to study pollutants emanating from the Mkabela Catchment in South Africa. The developed ACRU-NPS model included sufficient process details to allow for the implementation of controls such as wetlands, dams and buffer strips. Successful simulation of crop yields, nutrient and sediment production, together with the fate of NPS pollutants, for various land uses was thus achieved. The major contribution of this study however was to link hydrology and NPS pollution processes by describing and defining pathways through which pollutants moved in the catchment. This was achieved through studying the dynamics and connectivity of water, sediments and nutrient fluxes by combining hydrometric, hydropedological, geophysics and stable water isotope techniques to interpret the field and laboratory data. Suggestions for future improvements on the ACRU-NPS model were given based on the understandings gained from the different observations and sampling done in the Mkabela Catchment

Alternative screening method for drought tolerance in barley genotypes

Lack of genetically stable and durable drought tolerant winter and spring barley genotypes is one of the main contributing to low and unpredictable yields in Kenya and other parts of the world despite annual release of new and high yielding varieties. Therefore, the study was set to identify genotypes exhibiting tolerance to drought through physiological and phenotypic approaches. A total of 32 genotypes were planted in split-plot arrangement in completely randomized design replicated thrice. Genotypes were maintained under 20% and 80% field capacities. Phenotypic and physiological data were collected, converted to ratios then analyzed on Genstat version 14.1 VSN International Ltd at a 5% level of significance. Significant differences were observed in winter and spring barley in terms of growth, tillering ability, grains formed per spike, 1000 seed weight and MSI (p < 0.05). Spring barley expressed higher tolerance to drought than winter barley especially in terms of height, number of grains per spike and seed weight. Water deficiency in cells and tissues might have altered and inhibited physiological and biochemical processes. The phenotypic and physiological methods corresponded and confirmed tolerance to drought in most winter and spring genotypes grown in Kenya

Fingerponds: seasonal integrated aquaculture in East African freshwater wetlands : exploring their potential for wise use strategies; Proefschrift Wageningen Universiteit.

Wetlands play an important role in the livelihoods of many rural households particularly in sub-Saharan Africa. However, due to decline in rainfed terrestrial agriculture, many wetlands are being encroached upon to grow crops. The question to any wetland scientist/policy maker in the region is: what efforts can be made to achieve a balance between human needs for food and income and maintenance of ecosystem integrity?.This study analyses the potential of smallholder integrated aquaculture farming systems (called ""Fingerponds"") around the Lake Victoria wetlands in Kenya. Various analytical tools were used to evaluate the biophysical suitability, nutrient flows, benefits and environmental implications of this innovative technology.The critical biophysical factors determining Fingerponds productivity are site selection and water supply. The analysis of nutrient flows in the entire agroecosystem using nitrogen as the currency indicated that the total system throughput, and hence the overall productivity of the system were low. Fingerponds contributed to household livelihoods by providing protein and income and added diversity to the household activities with minimal impacts on the natural environment. With careful implementation and adaptive management, Fingerponds can be incorporated into national wetland policies and enhance the balance between economic development and environmental conservation

Conservation of highland streams in Kenya: the importance of the socio-economic dimension in effective management of resources

Conservation of streams in Africa cannot be considered separately from their importance as water sources for local people.  Humans and livestock interact daily with flowing water and its associated riparian vegetation, giving these landscape features social and economic importance.  Despite the destruction that these activities cause, they provide opportunities for imaginative approaches to conservation.  Issues focusing on resources other than water itself should be considered; for example, use of riparian vegetation for collection of medicinal herbs, firewood, timber for construction and as sites for spiritual, cultural and recreational activities.  To address these concerns, Kenyan streams and their catchments are given as examples in this paper, with the assumption that they are typical of streams and catchments in many parts of Africa.  These streams are used extensively for small scale abstraction, washing, livestock watering and exploitation of riparian vegetation.  All of these activities occur with little regulation or management, despite the riparian zones nominally being protected government property.  Effective management requires an understanding of patterns of supply and demand for water, which is seasonal, and for vegetation resources, which is continuous and increasing.  Challenges for effective management are identified as: politically- and tribally-mediated insecurity; ineffective governance, particularly with respect to enforcing protective legislation; different use of resources by different ethnic groups; division of labour along gender and age lines; poverty and the inability to diversify resources; traditions and neglect of traditional ecological knowledge; and inadequate formal education.  We propose that effective conservation of water and riparian resources – and therefore of essential ecosystem services – is best achieved by a combination of law enforcement and engagement of local communities with the resource upon which they depend.  Understanding the importance of the resource and engendering a spirit of community ‘ownership’ will help to avoid the current ‘tragedy-of-the-commons’, in which uncontrolled exploitation is increasing in a totally unsustainable fashion in tropical Africa

The effect of seasonal flooding and livelihood activities on retention of nitrogen and phosphorus in Cyperus papyrus wetlands, the role of aboveground biomass

With growing demand for food production in Africa, protecting wetlands and combining increased agricultural production with conservation of the ecological integrity of wetlands is urgent. The role of aboveground biomass of papyrus (Cyperus papyrus) in the storage and retention of nitrogen (N) and phosphorus (P) was studied in two wetland sites in East Africa under seasonally and permanently flooded conditions. Nyando wetland (Kenya) was under anthropogenic disturbance from agriculture and vegetation harvesting, whereas Mara wetland (Tanzania) was less disturbed. Maximum papyrus culm growth was described well by a logistic model (regressions for culm length with R2 from 0.70 to 0.99), with culms growing faster but not taller in Nyando than in Mara. Maximum culm length was greater in permanently than in seasonally flooded zones. Total aboveground biomass was higher in Mara than in Nyando. The amounts of N and P stored were higher in Mara than in Nyando. In disturbed sites, papyrus plants show characteristics of r-selected species leading to faster growth but lower biomass and nutrient storage. These findings help to optimize management of nutrient retention in natural and constructed wetlands