Harmful Algae Blooms (HABs) in inland waterbodies (e.g., lakes and ponds) pose serious threat to human health and natural ecosystem. Thus, it is imperative to assess HABs and their potential triggering factors over broader spatiotemporal scales. This study utilizes Chlorophyll-a (Chl-a) concentration in water samples collected from lakes in Illinois as an indirect measurement of HABs. The major objectives were to assess the spatiotemporal pattern of HABs over Illinois regions in recent decades, and to examine different machine learning models for predicting the Chl-a concentration based on publicly available water quality datasets. The Chl-a dataset was compiled from two different sources, the regular monitoring program by Illinois Environmental Protection Agency (IEPA) and the Voluntary Lake Monitoring Program (VLMP), the latter of which was primarily collected by citizen participants. Seven environmental and water quality zones were selected for spatial analyses. Additionally, the temporal patterns were assessed using time-series decomposition of monthly Chl-a concentration datasets. The machine learning pipeline includes two tasks: a regression modeling task for predicting Chl-a concentration, and a classification task for estimating lake trophic status. Different meteorological, land use and land cover, and lake morphometry variables were used as independent variables. Four regression models, i.e., Partial Least Squares Regression (PLSR), Support Vector Machine Regression (SVR), Artificial Neural Network Regression (ANNR), and Random Forest Regression (RFR) were used for the first task of the modeling pipeline, and four classification models, i.e., Logistic Regression Classification (LRC), Support Vector Machine Classification (SVC), Artificial Neural Network Classification (ANNC), and Random Forest Classification (RFC), were used for the second task. Results indicate that: a) the Collinsville region in southwestern part of Illinois exhibited higher mean concentration of Chl-a in its lakes than any other regions from 1998 to 2018; b) the lakes that showed increasing trends in their monthly mean Chl-a concentrations were also clustered in the southwestern region; c) Random Forest outperformed all other models in both classification (Accuracy=60.06%) and regression (R2=38.88%); and d) the land use and land cover variables were found as the most important set of variables in Random Forest models.

Access to a safe drinking water supply is a critical issue in a number of places across the globe. Conventional water quality monitoring technologies are slow, often taking at least two days to produce results. In recent years, there has been extensive research into emerging technologies that provide real-time results; however, there is no technology which detects all classes of biological contaminants. Biological contaminants are 5 particularly difficult to detect and quantify due to low concentrations typically present. It is not feasible to identify all biological contaminants present in a water supply; therefore, it is necessary to determine which are of highest concern based factors such as health significance, infectivity, and prevalence. The intent of this research is to evaluate microbiological detection methods and technologies based on their applicability for continuous real-time detection. This research will complement current research on biological water quality monitoring technologies for use in developing regions or in the event of an emergency and will provide suggestions for future research efforts.

The 178,000-acre Grassland Ecological Area in California’s San Joaquin Valley is managed to provide overwintering habitat to waterfowl on the Pacific Flyway. The major management activity is the fall flooding and spring drawdown of wetlands, timed to optimize the availability of forage vegetation and invertebrates for ducks and shorebirds. Wetland drainage contains salt, boron, and trace elements that are, in part, derived from imported surface water but also concentrate during storage in the wetland impoundments. The spring drawdown drainage contributes to occasional water quality violations in the San Joaquin River (SJR) during dry years. Compliance with water quality objectives may be improved by delaying the traditional wetland drawdown period approximately one month to coincide with high SJR salt assimilative capacity during mid-March to mid- April when reservoir releases are increased to aid salmon migration. However, this delayed drawdown may affect the quality and quantity of wetland vegetative forage, increase wetland soil salinity, and possibly alter the concentrations of algae, invertebrates, and pollutants in the wetlands. In the research presented herein, initial data were collected on the effects of delayed drawdown on algae, invertebrates, and wetland water quality. The experimental sites chosen were three pairs of matched wetland basins (20-100 acres each) that are part of the larger Modified Hydrology Study being conducted in the Grassland Ecological Area. For each pair, one wetland was managed with a traditional March drawdown; while for the second wetland, drawdown was delayed approximately one month to coincide with the period of high SJR assimilative capacity. During the second year of the study, two drainage sites were sampled to characterize drainage flowing to the SJR from an aggregated wetland area. Soil and water column samples were collected during the flooded periods at the inlets, outlets, and along transects within the wetlands. Water quality analyses included total/volatile suspended solids, conductivity, nitrogen (NH4 +, NO2⁻+NO3⁻, organic), phosphorus (total, PO4 3-), organic carbon, alkalinity, turbidity, temperature, and pH. Planktonic and benthic invertebrates were identified and enumerated. Data were collected between February and April in 2007 and again in 2008. Identified phytoplankton were predominantly chlorophytes and diatoms. Zooplankton that feed on phytoplankton were found in abundance and consisted mostly of Cladocera. Benthic invertebrate densities were also measured to help explain the differences in algal concentrations between ponds. Benthic invertebrates were found to be predominantly Chironomidae. Seasonal loads of volatile suspended solids, total dissolved solids, and total organic carbon were estimated at the two aggregate drainage sites and at one delayed drawdown wetland during the 2008 season. For volatile suspended solids, the discharged load was 1500 lbs at the Buttonwillow drainage site, 2500 lbs at the Los Banos 38 drainage site, and upstream of those sites, 770 lbs were discharged from the Mud Slough 4b wetland. For total dissolved solids, the discharged load was 290 tons, 520 tons, and 26 tons, respectively, for the same locations. Of the factors potentially limiting phytoplankton concentrations, invertebrate grazing was likely the most important. Nutrients were not limiting in either the traditional or modified wetlands, as indicated by sufficient N and P content in the algae biomass. Likewise, inorganic C was not limiting, as indicated by pH (most <9.0 pH). Sunlight intensity was not significantly attenuated by water depth or turbidity, and thus light limitation was not indicated.

Dans le contexte péri-urbain à dominance agricole de l’Ile de France, les pressions anthropiques exercées sur les rivières jouent autant sur la qualité que sur le débit des cours d'eau. Située au sud-ouest de Paris, l’Yvette draine un bassin versant de 202 km²et à la géologie homogène. Elle est alimentée directement par des stations d'épuration (STEP) et par la nappe des sables de Fontainebleau qui représente la principale source d’eau. Sur ce type de bassin, la gestion durable du système riverain repose sur la connaissance de la distribution des flux nappe – rivière et sur l’impact de cette répartition sur la qualité des cours d’eau.La dynamique des flux d’eau a été suivie grâce à l’implantation de stations hydrométriques aux points clés du réseau hydrographique (i.e. exutoires des principaux affluents, aval des confluences sur l’Yvette). Les flux chimiques ont été étudiés par analyses d’échantillons d’eau recueillis lors de campagnes de terrain effectuées en période d’étiage sur les cours d’eau. Un modèle conceptuel global, calibré à partir des chroniques de débit, a permis (i) d’estimer des variations spatiales de la recharge de la nappe (60 – 160 mm.an-1), et (ii) d’établir une répartition journalière des parts d’eau de nappe, de STEP et de ruissellement en rivière, pour la période 2001-2014. Par ailleurs, l’analyse des traceurs géochimiques (e.g. Cl-, NO3-, SO42-) et isotopiques (222Rn, δ18Oeau, δ2Heau) soutient la prédominance, aussi bien quantitative que qualitative, de la nappe sur les rivières.D’un point de vue hydrodynamique, le contexte géomorphologique homogène procure aux rivières une dynamique similaire avec des épisodes de crues très courts (de l’ordre de quelques heures) et des périodes d’étiages marqués, quelle que soit la saison. L’étude par sous-bassin a mis à jour une différence entre les bassins topographiques et les bassins d’écoulement souterrains, créant des déficits hydriques sur l’amont de certains cours d’eau (e.g. Mérantaise, Ru des Vaux) au profit d’autres (e.g. Rhodon). Le parallèle entre bassins topographique et souterrain n’a pu se faire qu’au niveau du cours principal de l’Yvette. Sur la période 2001-2014, le débit de l’Yvette provient en moyenne à 55 % de la nappe, à 38 % du ruissellement et à 8 % des STEP. En période de basses eaux, la contribution des STEP reste sensiblement identique tandis que la nappe constitue la principale alimentation des rivières (90 %), contrôlant donc leur qualité. Mais la composition chimique de ce soutien souterrain n’est pas homogène. Pour déterminer l’origine de ces disparités, un travail à plus petite échelle a été conduit sur un affluent majeur de l’Yvette (le Rhodon). La décharge de la nappe en rivière y est bimodale : 15 % arrive par voie souterraine et 85 % transite par les milieux humides en surface. Au sein des zones humides sont observées de fortes hétérogénéités dans les écoulements et leur chimie, avec des flux de subsurface totalement épurés en nitrates et du ruissellement riche en nutriments. La prédominance de des flux de surface réduit fortement le pouvoir épurateur des milieux humides, avec seulement 6 % des eaux de nappe épurées avant leur décharge en rivière. Cette faible efficacité renforce l’impact direct de la qualité de la nappe sur les rivières. Sur le bassin, la nappe est stratifiée par l’intervention de nombreux processus de recharge (infiltrations d’eau d’étang, de STEP, de zones humides de plateau). Les petits sous-bassins (< 50 km²) semblent dominés par cette stratification, ainsi que par les apports de STEP qui contribuent aux flux chimiques des rivières à hauteur de 30 à 50 %. Le cours principal de l’Yvette, dans sa partie aval, dépend des mélanges issus des confluences avec ses affluents. Les outils utilisés ici ont donc mis en avant les différences de fonctionnement des bassins selon l’échelle concernée, tout en reliant l’importance de la compréhension du système à petite échelle pour la gestion à grande échelle. / In the peri-urban context with large farm practices of the Paris region, anthropogenic pressures on streams and rivers impact both their flow and quality. Located in the southwestern of Paris, the Yvette stream drains a watershed of 202 km², in a homogeneous geological context. The stream is sustained by waste water treatment plant (WWTP) and by the Fontainebleau sands aquifer which represents the main source of water.In this context, the sustainable management of the stream and its riparian zones needs the assessment of groundwater discharge locations and chemistry, and their impact on the stream water quality.Water fluxes in the stream and in its main tributaries have been recorded at 11 stations. Dissolved elements distributions have been studied by field works in low-flows conditions. A lumped model, calibrated with stream flow hydrographs, has allowed (i) the estimation of groundwater recharge rates (60 – 160 mm.y-1) and (ii) the distribution of stream flow contributions between 2001 and 2014 (i.e. 55 % from groundwater, 38 % from runoff and 8 % from WWTP). Moreover, the use of geochemical and isotopic tracers (e.g. Cl-, NO3-, SO42-, 222Rn, δ18Owater, δ2Hwater) confirmed the large impact of groundwater on stream flow and quality.The hydrological dynamics of the Yvette stream and its tributaries are similar because of the homogeneity of the geomorphological context of the catchment. The flood events are really fast (on the order of hours) and low-flow conditions can be observed in every season. The discretization of the Yvette catchment in 11 sub-watersheds highlighted a divergence between the topographical and hydrogeological catchments. This generates a water deficit in some tributaries heads (e.g. Mérantaise, Ru des Vaux) in favor of some others (e.g. Rhodon). The matching limits of these catchments can only be made on the Yvette channel. During the 2001 – 2014 period, considering a fairly constant WWTP contribution, the groundwater discharge provides more than 90 % of the stream flow during low-flow conditions. This highlights a stream quality dominated by groundwater discharge. However, groundwater chemistry largely varies over the catchment. To study this phenomenon, a small-scale field work has been directed on the Rhodon stream, a main tributary of the Yvette River. At this scale, the groundwater discharge appeared to have two main pathways: 15 % come from the streambed while 85 % transit in wetlands before going to the stream. Within these wetlands, a large part of groundwater flows at the surface and has high levels of nutrients, whereas a small part (6 %) goes through sediments and is nutrients free. reduces The purifying power of these wetlands, significantly reduced by this distribution, is likely related to historical drainage and reinforces the direct connection between the stream and groundwater quality. On the Yvette catchment, the stratification of groundwater chemistry is due to several recharge processes (e.g. pond water infiltration, WWTP effluents infiltration, wetlands water infiltration). Small sub-watersheds (< 50 km²) seem to be dominated by (i) this stratification, and (ii) the WWTP discharges which can contribute from 30 % to 50 % to dissolved fluxes in the streams. The main channel of the Yvette stream primarily depends of the mixing of its tributaries waters. The methods developed here allowed highlighting (i) differences of catchment functioning according to the scale used, and (ii) the utmost importance of the small-scale assessment to understand/decipher and manage streams at larger scales.

The paradigm shift in water quality management of South African water resources was based on current international trends. This significant move was from a previous emphasis on source management to a focus on finding a balance between water resource protection and water use. The current approach requires that water quality and quantity should be maintained for sustainable functioning of both the natural aquatic environment and socioeconomic development. This approach has placed the assessment of water quality status as a key decision tool in water quality management. Various assessment tools have been utilized to quantify the quality of South African water resources. In this study we assessed the compatibility of some of the methodologies that have been used in the Department of Water Affairs to determine and report on the water quality status of the resource. During the assessment the context and manner in which these methodologies can be utilized in water quality management were also addressed The Compliance Evaluation and Fitness for use categorization methodologies are both used to describe the water quality threshold of potential concern when dealing with the resource. Compliance Evaluation methodology uses a pass or fail assessment, while the Fitness for use categorization methodology uses a scaled approach allowing for the assessment of gradual change in the system. The out puts of these two methodologies, the Resource Water Quality Objectives and Fitness for use categories/ classes have both been used in the department as benchmarks to describe the current water quality status The assessment of the two methodologies indicated that there are similarities in the approaches and the principles behind the two processes. The observation of the results, however, indicated differences in the manner of presentation of the results, the interpretation of the outcome and in how water quality management measures that needs to be implemented are linked. Both methodologies are easy to apply when conducting water quality status assessments. However, the two methodologies are not sufficient on their own when making decisions on water quality management. It was concluded that although the compliance evaluation methodology can play a pivotal role when setting end of pipe standards, the process needs to consider the gradual changes of water quality in the river system in order to enable instigation of different water quality management measures at appropriate levels. Further it was recommended that with some modification the two approaches can be applied to assess water quality to support adequate water quality management decisions at various levels. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Animal and Wildlife Sciences / Unrestricted

MENVSC / Department of Ecology and Resource Management / Satellite remote sensing techniques have been proved to be the best methods for quantifying chlorophyll-a levels by estimating algal concentrations in water bodies. Harmful algal blooms (HABs) are posing a significant threat to the many water bodies in South Africa. This study aims at developing remote sensing solution to estimate chlorophyll concentrations in water bodies of Vhembe district municipality using recently launched Landsat 8 OLI. It is the first study to provide quantitative water quality information for the Vhembe region’s water bodies from a time series of satellite remotely sensed data and in-situ laboratory data. The objectives of this study was to evaluate spatial and temporal distributions of algae in water bodies and fish-ponds, to assess water quality parameters, namely: chlorophyll-a and turbidity and to compare data obtained from satellite remote sensors with in situ data. The 30 meters spatial resolution multispectral Landsat 8 OLI for 2016, 2017 and 2018 were used to derive chlorophyll-a estimate from an existing model at three water bodies. The chlorophyll-a concentrations measured during in-situ were employed to validate the Landsat derived chlorophyll-a estimates. The results from this study shows that Landsat derived chlorophyll-a estimates are correlating with field measurements. In all the reservoir, it was detected that there is low content of harmful algal blooms and thus the water bodies are in good condition since the chlorophyll-a concentrations were very low (ranging from 0 to 0.6 mg.m-3). In conclusion, it can be stated that Landsat 8 OLI sensor has the potential to map inland water bodies dominated with algal blooms at certain extent. It can further be stated that Landsat 8 OLI is suitable for monitoring the growth of HABs in aquatic ecosystem and is cost effective. This study also evaluated the potential of Banana peels powder and K2SO4 to inhibits the growth of algae (batch experiment). The water samples were collected at Tshifulanani and Lwamondo fish ponds where there are floating algae. The samples were collected seasonally and analysed for pH, water temperature, Total Dissolved Solids, Electrical conductivity, Dissolved Oxygen, turbidity, chlorophyll-a and absorbance. From the laboratory experiments, there was a variation in the values of absorbance (0.936A-1.234A), PH (7.1-8.3), EC (63.1- 87.9 μs/cm), TDS (52.6-69.7mg/L), water temperature (25.5-29.3°C) and Dissolved oxygen (5.3-7.1mg/L). The concentration of chlorophyll-a for Tshifulanani and Lwamondo fish ponds ranges were (2.14-15.96 mg/m-3) and (0.65-15.66 mg/m-3) respectively. A batch experiment was conducted to determine the potential of banana peels powder on inhibition of algal blooms in water samples by measuring absorbance at 750nm. It can be concluded in this study that banana peels have a potential to inhibits the growth of algae in fish ponds. The Absorbance has shown a rapid v decrease from 0.936A to Zero from day 1 to day 7 respectively. The inhibition of cyanobacteria by banana peels is followed using Potassium sulphate in treating the algal blooms in water samples. Both banana peels and potassium Sulphate has shown a positive response in treatment of algae on the batch experiment. The results of this study revealed that high concentration of physico-chemical parameters promote the growth of cyanobacteria in fish ponds but does not have negative effects on the fish except the oxygen competition with algal blooms. The statistical analysis in correlating the chl-a field measurements and remotely sensed data showed a positive outcome where K values were very high from 70% to 89%. These results show high level of agreement of correlation values of field chlorophyll-a concentration and satellite remotely sensed variables. / NRF

Lake Ringsjön, located in south of Sweden, has been subject of eutrophication since 1950s and received several restoration efforts. Latest restoration effort, “Project Ringsjön”, was proposed in 2003 to improve lake condition against eutrophication by reducing nutrient concentration. This study was done to assess the nutrient loading into the lake from the catchment of Hörbyån Creek, which is discharging into the lake from southeast. Study addresses the nutrient loading conditions from Hörbyån Creek before and after the implementation of “Project Ringsjön” in 1998 and 2010 respectively. Thus a water quality analysis was performed to observe the changes in total nitrogen and total phosphorus concentration in Hörbyån Creek between these years. Effort was also made to investigate nutrients contribution of different watersheds in the catchment. This study also addresses the effect of seasonal variability and land use on nutrient loading. In order to achieve objectives, annual and monthly water quality modelling was performed on the river. HEC-RAS software was used to simulate water quality variables loading from catchment into the lake, such as nitrates, nitrite, ammonium, organic nitrogen, inorganic phosphorus and orthophosphate. Results indicated increase in average annual total nitrogen concentration from 4.18 mg/l to 4.56 mg/l and reduction in average annual total phosphorus concentration from 0.165 mg/l to 0.083 mg/l in the water discharging into the lake from catchment. The watershed occupying mostly agriculture area was observed to have maximum nutrients contribution, which might be due to high fertilizer leakage. It was also observed that maximum nutrient loading was taking place in November and March; probably due to high runoff generated from precipitation and snow melting that carried additional nutrients to the water bodies. Results also indicated that the studied catchment area was contributing high nutrient concentration for eutrophication in both years; however, there was small decrease in total phosphorus concentration in 2010 compare to 1998.

Detection of unexpectedly high concentrations of agricultural pollutants in ground water have inspired investigations of the role of preferential movement of chemicals through agricultural soils. This research focuses on preferential flow and solute transport processes and the effects of agricultural management practices on these processes. Experimental methods for monitoring preferential flow and solute transport in the field as well as a stochastic, physically-based model for predicting water flow and transport of non-reactive chemicals in heterogeneous soils with naturally occurring macropores were developed and evaluated. Field experiments, aimed at monitoring the occurrence of preferential flow and solute transport, were conducted in a conventionally-tilled and a no-till soybean field in the Coastal Plain of Virginia. A rainfall simulator was used to apply a one-hour storm at rates of 5.0, 6.5 and 7.5 cm/hr to six 1.83 by 1.83 m plots. Chloride was added to the water to serve as a non-reactive tracer. Electrical conductivity equipment provided a useful method for monitoring solute transport. The moisture and solute conditions, observed during a 28-hour period after the start of the rainfall event, clearly indicated the occurrence of preferential flow and solute movement in the field plots. The variability of the solute concentrations in the field plots was generally higher in the no-till plots than in the conventionally-tilled plots. The plots that received rain at 6.5 and 7.5 cm/hr showed more variability than the plots that received rain at 5 cm/hr. The observed solute concentrations indicated that if the solute transport would have taken place by advection only, 61% of the solute transport in the conventionally-tilled plots and 50% of the solute transport in the no-till plots could be attributed to preferential flow. A physically-based, finite element model for simulating flow and solute transport in variably-saturated soils with macropores (MICMAC) was developed. Flow and solute transport are described by the Richards' equation and the convection-dispersion equation. Flow in the macropores is described by the Hagen-Poiseuille equation. An axisymmetric coordinate system is used to simulate the flow and solute transport from the macropore into the surrounding soil matrix, assuming a vertically oriented, surface-vented, cylindrical macropore. Flow and solute transport between the macropore and the soil matrix are driven by the pressure head at the macropore-matrix boundary. To assess the natural heterogeneity of the soil properties a stochastic component was added to the model. Flow and solute transport at the field scale were simulated by regarding the field as a collection of statistically independent, non-interacting vertical soil columns, using Monte Carlo simulation. The sensitivity analysis of the model indicated that, for a soil with macropores, the model is most sensitive to the saturated water content of the soil matrix, the initial moisture content, and the rainfall rate. The model is not very sensitive to the macropore dimensions. Examination of the stochastic approach indicated that the representation of a heterogeneous field as a collection of non-interacting stream columns may substantially underestimate water and solute leaching. A change of 5% in the soil properties of the neighboring soil columns may underpredict the solute leaching, 24 hours after a rainstorm, by 157% for a soil column with a macropore, and by 58% for a soil column without a macropore. These differences decreased to 47% and 8%, respectively, 168 hours after the rainfall. Field application of the model suggested that the model underestimates the leaching of water and solutes from the root zone. However, the computed results were substantially better than the results obtained when no preferential flow component was included in the model. The model performed best under conditions that favored preferential flow, i.e., a high rainfall rate and high initial moisture conditions. The simulated and observed solute concentrations in the root zone agreed reasonably well, although the maxima of the observed data were generally higher than those of the simulated data. / Ph. D.

Taste-and-odor (T&O) compounds are frequently produced by cyanobacterial blooms in bodies of water. Geosmin, perhaps the most common T&O compound produced by these blooms, is not effectively removed by conventional water treatment processes and frequently causes the tap water to have an off flavor. Although geosmin is not harmful when ingested, it damages the consumers' confidence in the cleanliness of their water. There are treatment options for geosmin removal, but the most common methods are often not implemented until complaints are made by consumers.There has been an increasing amount of research on the use of polymerase chain reaction (PCR)-based methods that can detect the presence of the geosmin synthase gene which is responsible for the production of geosmin. If the geosmin synthase gene is found to be present in an emerging cyanobacterial bloom, water treatment facilities can prepare in advance to treat for geosmin. In this study, we developed a qPCR (quantitative polymerase chain reaction) assay that can detect the presence of the geosmin synthase gene in several species of cyanobacteria within the Anabaena genus. We tested our assay, as well as PCR assays designed by Giglio et al. (2008) and Suurnäkki et al. (2015) on extracted Anabaena flos-aquae DNA, biosynthesized Anabaena ucrainica DNA and DNA extracted from environmental samples of Deer Creek Reservoir, Strawberry Reservoir, and Utah Lake. It is important to note that the geosmin gene was not confirmed to be present in any of the environmental samples nor in the Anabaena flos-aquae DNA and our assay did not test positive on these samples. Our qPCR assay was very successful when used with the biosynthesized Anabaena ucrainica DNA. We used the results to estimate a DNA standard curve that can be used to estimate the starting concentration of the geosmin synthase gene. Because our assay was not successfully used with any extracted DNA, further testing and calibration may be necessary to produce a DNA standard curve that is representative of DNA that is extracted. Further calibration of the DNA standard curve was not done because there were no geosmin events during the course of the research.Development of PCR-based methods of detecting geosmin-producing cyanobacteria requires genetic sequencing information of the target-organisms. Thus, further development of PCR-based methods requires that the local geosmin-producers be identified and sequenced. Our assay as well as the assay designed by Moore (2019) can assist with the identification of these species by classifying their genus.

Palustrine wetlands in Lesotho are vulnerable to vegetation loss due to overgrazing and the nature of the topography, the latter leading to gully erosion exacerbated by a degraded soil structure. Degraded soils are not able to adsorb pollutants; neither can they support vegetation growth. The presence of degraded soils in wetlands thus contributes towards leaching of pollutants into nearby streams and groundwater resources. Khubelu wetland (which was the focus of this study) is a palustrine wetland that discharges water into the Khubelu stream in Lesotho. The water purification function of this wetland is pertinent since Khubelu River is one of the tributaries at the headwaters of the shared Orange- Senqu basin. This function is threatened by vegetation loss and soil degradation through overgrazing and environmental conditions like extreme climatic variations. Consequently, water released into adjacent streams from the wetland could be of low quality, further putting at risk the health of this ecosystem and users of these streams due to toxicity caused by the polluted water from the wetland. With predicted floods and/or droughts and intense heat, water temperatures may rise by up to 70% in the 21st century according to researchers. It is believed that floods would lead to shorter residence time of water within wetlands, washing away soil with pollutants into surrounding streams before any geochemical processes that would sequester them occurs. Droughts on the other hand would lead to failure of dilution of polluted waters. Excessive evaporation due to intense heat would also leave pollutant-concentrated water behind. Since these wetlands are the headwaters of an international river, the problem of water pollution and deteriorated water resources might be regional. The main aim of the study was to characterise the extent of soil degradation and water quality in the Khubelu wetland and assess the water purification ability in an endeavour to understand the role the wetland plays in the quality of water in rivers and streams fed by the Khubelu wetland, and also to understand how changes in climate would impact on the wetland characteristics. In situ analyses of soil and water were done followed by sampling of the same for further analysis in the laboratory using standard methods. Surface water samples were collected from two sampling points in the Khubelu stream, whereas water in the wetland was sampled from seven piezometers installed in the wetland. Three replicates of water samples were collected from each sampling point monthly over a period of one year. The water properties determined included pH, Electrical Conductivity (EC), Dissolved Oxygen (DO), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), cations (magnesium, calcium, potassium and sodium), Total Dissolved Solids (TDS), nitrates, phosphates and chlorides. The data generated from these analyses were subjected to various statistical tests and the Water Quality Index (WQI) of the wetland and stream waters determined. The water quality drinking standards were preferred in this study since the major beneficiaries of the stream that emanates from the wetland are human populace. Prediction of water quality in the wetland in light of the changing climate was done using the Water Evaluation and Planning (WEAP) model. Soil samples were collected from the upper, middle and lower areas of the wetland, referred to as upstream, midstream and downstream of the wetland in the report, at the same sites where the piezometers were installed. At each site, three sampling points were identified two metres apart from each other and samples collected at depths of 15 cm, 30 cm and 45 cm at each site. The soil samples were then characterised for their texture, pH, Electrical Conductivity (EC), Cation Exchange Capacity (CEC), Total Carbon (TC), Total Nitrogen (TN), Organic Matter (OM), exchangeable calcium, magnesium, potassium and sodium, and available phosphorus, using standard procedures. The soil data generated were then subjected to data analyses and the Chemical Degradation Index (CDI) of the wetland soils determined. Determination of the wetland’s potential to purify water was done by assessing its ability to retain nutrients, pollutants and sediments. Results obtained in this study showed that the wetland and stream water had circumneutral pH with values that ranged from 6.32 -7.69. The values for Na, Ca, K, Mg, TDS, NO3, Cl and DO in the wetland and stream waters were below the WHO drinking water standards thresholds of 200 mg/l for Na and Ca, 12 mg/l for K, 150 mg/l for Mg, 50 mg/l for TDS 50 mg/l for NO3, 5 mg/l for DO and BOD, and 250 mg/l for Cl. Food and Agricultural Organisation (FAO) water standards for livestock drinking were: EC: <1.5 mS/cm (Excellent); 1.5 – 5.0 mS/cm (very satisfactory); < 250 mg/l of Mg for cows, 400 mg/l for beef cattle, and 500 mg/l for adult sheep. SA Irrigation water quality standards were also used, and it was determined that pH was within the acceptable threshold of 6.5 – 8.4, 70 mg/l for sodium and 0.4 mS/cm for EC. EC of 0.41 mS/cm to 1.12 mS/cm in the wetland and 0.67 mS/cm to 2.11 mS/cm in the stream was above the SA irrigation water quality standards. Other water properties such as PO4 (0.06-1.26 mg/l in stream and 0.17- 0.61 mg/l in wetland), and COD (10.00 to 55.00 mg/l in stream and 48-140.80 mg/l in the wetland) were above the WHO permissible limits. The water quality in the Khubelu wetland and stream ranged from very poor to unsuitable for drinking, with WQI values of 107 for the stream and 93 for the wetland. Water quality simulation along the Khubelu stream using the WEAP model shows that by the year 2025, BOD as one of the water quality parameters, would be high, with DO declining further especially if temperature increases and precipitation decreases. The wetland had sandy and acidic soils, with the TC and TN content of the soil decreasing with depth. The CDI value for the soil was 3.29. Regarding potential to reduce sediments, nutrients and organic pollutants, the wetland scored 7.09, 5.39 and 7.39 out of 10, respectively. This implies that there is moderate potential for the wetland to purify water that is discharged into the stream. The study concludes that the stream and wetland water qualities are unsuitable for human consumption and usable for livestock drinking. However, there might be some risks associated with evaporation that would leave the water saline. The wetland water presents a threat to the water quality of the receiving stream. However, the wetland has moderate potential to retain sediments, nutrients and toxic organics. This potential is threatened by a predicted decrease in precipitation and increase in temperature since oxygen-depleting contaminants and other pollutants whose behaviour in the environment are influenced by climate are highly likely to increase in concentrations in both the wetland and the stream. There is therefore a threat to the supply of water of good quality to the Senqu catchment, which supplies neighbouring countries (South Africa, Namibia and Botswana). Similar studies to this one need to be carried out for other wetlands in Lesotho on a regular basis to come up with data that would aid policy development that seeks to protect water resources. / Environmental Sciences / D. Phil. (Environmental Management)