Evaluation of Surface Energy Balance System (SEBS) Model for Estimation of Evapotranspiration in Eastern Ethiopia

Quantification of evapotranspiration (ET) is needed for a wide array of applications especially for water resources management. ET estimation by using either ground based direct measurement or modeling by using in-situ based meteorological variables is found cost inefficient or for some geographic areas it might be impractical. This issue is specially challenging in data scarce regions. This study evaluates remote sensing based surface energy balance system (SEBS) in arid and semi arid eastern Ethiopia. After undertaking a series of pre-processing and processing phases, surface parameters has been generated from MODIS level 1B products for dry season and dekadal composites from spot vegetation, down welling surface short web flux from LSA SAF and near surface meteorological variables from GLDAS has been utilized. By ingesting these parameters at prepackaged SEBS model, ET has been estimated. For comparative analysis, MSG ET with FAO-PM has been utilized. Our findings have shown that estimated ET ranges from 0 to 10 mm day -1 with large spatial variability. In areas that are well vegetated, SEBS provides larger values both at dry and wet seasons but at arid and semi-arid vast expanses of the study site there is found very lower ET value at dry season and increases with vegetation regeneration in the summer season. It was observed that at both dry and wet seasons SEBS ET values were over estimated than MSG ET product and underestimated than FAO-PM values. These under and over estimations were very large at arid and semi-arid areas which is attested from point based analysis undertaken using meteorological stations located at different climatic characteristics. Our study confirmed that, though SEBS model provides reasonable results it is sensitive for vegetation cover of a site. Taking these into consideration there should be comparative analysis of the model with direct field measurements for more certainty. Keywords: Evapotranspiration, Eastern Ethiopia, SEBS, Remote sensin

An Intercomparison of Satellite-Based Daily Evapotranspiration Estimates under Different Eco-Climatic Regions in South Africa

Knowledge of evapotranspiration (ET) is essential for enhancing our understanding of the hydrological cycle, as well as for managing water resources, particularly in semi-arid regions. Remote sensing offers a comprehensive means of monitoring this phenomenon at different spatial and temporal intervals. Currently, several satellite methods exist and are used to assess ET at various spatial and temporal resolutions with various degrees of accuracy and precision. This research investigated the performance of three satellite-based ET algorithms and two global products, namely land surface temperature/vegetation index (TsVI), Penman–Monteith (PM), and the Meteosat Second Generation ET (MET) and the Global Land-surface Evaporation: the Amsterdam Methodology (GLEAM) global products, in two eco-regions of South Africa. Daily ET derived from the eddy covariance system from Skukuza, a sub-tropical, savanna biome, and large aperture boundary layer scintillometer system in Elandsberg, a Mediterranean, fynbos biome, during the dry and wet seasons, were used to evaluate the models. Low coefficients of determination (R2) of between 0 and 0.45 were recorded on both sites, during both seasons. Although PM performed best during periods of high ET at both sites, results show it was outperformed by other models during low ET times. TsVI and MET were similarly accurate in the dry season in Skukuza, as GLEAM was the most accurate in Elandsberg during the wet season. The conclusion is that none of the models performed well, as shown by low R2 and high errors in all the models. In essence, our results conclude that further investigation of the PM model is possible to improve its estimation of low ET measurements

Satellite-based analysis of recent trends in the ecohydrology of a semi-arid region

We present a regional framework for an integrated and spatiotemporally distributed assessment of human-induced trends in the hydrology and the associated ecological health of a semi-arid basin where both human activities (i.e. agriculture) and natural ecosystems are highly groundwater dependent. To achieve this, we analysed the recent trends (from year 2000 to 2010) in precipitation, evapotranspiration (actual and potential) and vegetation greenness (i.e. NDVI) using a combination of satellite and ground-based observations. The trend assessment was applied for the semi-arid Konya Basin (Turkey), one of the largest endorheic basins in the world. The results revealed a consistent increasing trend of both yearly evapotranspiration (totally 63 MCM yr−1 from croplands) and mean NDVI (about 0.004 NDVI yr−1 in irrigated croplands), especially concentrating in the plain part of the basin, while no significant trends were observed for the precipitation and potential evapotranspiration variables. On the contrary, a consistent decreasing trend of both yearly evapotranspiration (totally −2.1 MCM yr−1) and mean NDVI (−0.001 NDVI yr−1) was observed in the wetlands, which also cannot be explained by trends in precipitation and potential evapotranspiration. The emerging picture suggest that the greening trend of the vegetation and increasing of evapotranspiration in the plain are related to land cover changes (i.e. conversion into irrigated croplands) and to the intensification of the supplementary irrigation for agriculture, which in turn caused drying out of some wetlands and the natural vegetation which mostly depend on the groundwater, the main source of irrigation water as well. Our study presented an example of the utility of spatially and temporally continuous RS data in assessing the regional trends in hydrological and ecological variables and their interactions in a spatially distributed manner in a semi-arid region, which can also be adapted to other regions. Such spatiotemporally distributed analysis at the basin level is particularly important considering that most of the water management interventions also take place at this scale

Evapotranspiration estimation using Landsat-8 data with a two-layer framework

This work was partially supported by the National Natural Science Foundation of China (41401042), National Key Basic Research Program of China (973 Program) (Grant No. 2015CB452701) and National Natural Science Foundation of China (Grant Nos. 41571019 and 41371043).Peer reviewedproo

ET mapping for agricultural water management: present status and challenges

Evapotranspiration (ET) is an essential component of the water balance. Remote sensing based agrometeorological models are presently most suited for estimating crop water use at both field and regional scales. Numerous ET algorithms have been developed to make use of remote sensing data acquired by sensors on airborne and satellite platforms. In this paper, a literature review was done to evaluate numerous commonly used remote sensing based algorithms for their ability to estimate regional ET accurately. The reported estimation accuracy varied from 67 to 97% for daily ET and above 94% for seasonal ET indicating that they have the potential to estimate regional ET accurately. However, there are opportunities to further improving these models for accurately estimating all energy balance components. The spatial and temporal remote sensing data from the existing set of earth observing satellite platforms are not sufficient enough to be used in the estimation of spatially distributed ET for on-farm irrigation management purposes, especially at a field scale level (~10 to 200 ha). This will be constrained further if the thermal sensors on future Landsat satellites are abandoned. However, research opportunities exist to improve the spatial and temporal resolution of ET by developing algorithms to increase the spatial resolution of reflectance and surface temperature data derived from Landsat/ ASTER/MODIS images using same/other-sensor high resolution multi-spectral images

Ecohydrology in water-limited environment using quantitative remote sensing - the Heihe River basin (China) case

Water-limited environments exist on all continents of the globe and they cover more than 30% of the Earth’s land surface. The eco-environments of these regions tend to be fragile and they are changing in a dramatic way through processes like land desertification, shrinking of oases, groundwater depletion, and soil erosion. These are either human induced or results of a changing climate. Implications of these changes for both the regional hydrologic cycle and the vegetation have been documented. Since these changes occur over a wide range of scales in space and time, remote sensing methods are needed to monitor the land surface characteristics, to observe changes in vegetation and hydrological states, and to compare these with predictions from hydrological models. It is widely accepted that remote sensing methods offer the ability to acquire spatially continuous measurements over large areas. Remote sensing can also help to visualize complex processes because the spatial data can be captured regularly over time. China is one of several countries with large arid and semi-arid areas. The Heihe River basin, situated in the arid inland of northwestern China, is one of the areas severely affected by ecoenvironmental degradation and recovery. The problem of the degraded environment is due to overexploitation of surface and ground water leading to shrinking of oases, including the decline and death of natural vegetation, and the lowering of the groundwater table. Exhaustive (over-)use of water resources is the main cause of land degradation in the lower reaches of the basin, called the Ejina oasis. The whole Heihe River basin is therefore selected as study area in this thesis to analyze the long-term eco-environmental changes. What happens in this river basin is likely to have a growing influence on regional hydrological cycles, even affecting human life. Effective management of eco-environmental problems in this critical zone of water-limited conditions will provide scientific evidence for protecting and improving the eco-environment in these Chinese northwestern arid regions, eventually resulting in land improvement. Studies on quantifying the relationship between the vegetation and the water resources are a critical step in developing an ecohydrological approach to resources management in order to minimize environmental degradation. Remote sensing measurements can help us to better understand the effects of changes in water management on hydrological processes and their subsequent feedback to the eco-environment at the regional scale. Remote sensing methods can also provide information to quantify heterogeneity and change at a large scale. Therefore, the main objective of this thesis is to develop a methodology for the quantitative assessment of eco-environmental changes at a large scale in arid regions by integrating remote sensing methods in ecohydrological approaches. Chapter 1 outlines the significance of quantitative assessment of eco-environmental changes using remote sensing methods and applying them for ecohydrology in northwestern China, resulting in the specific research objectives of this thesis. Chapter 2 quantifies both the vertical and horizontal distribution of vegetation in the Qilian Mountains area, representing the upper reaches of the Heihe River basin, based on MODIS NDVI images from the year 2000 - 2006. Our analysis reveals that elevation and aspect are two important impact factors for the vertical distribution of vegetation in a mountainous area. The NDVI increases with the elevation and reaches a maximum value at a certain elevation threshold, and then decreases as the elevation increases beyond this threshold. The optimal vegetation growth is on the shady side of the mountains because of less evapotranspiration. The best combination of temperature and precipitation is assessed providing good conditions for vegetation growth. Chapter 3 presents an efficient method to estimate the regional annual evapotranspiration (ET) based on the SEBS algorithm (Surface Energy Balance System) in the Zhangye basin, representing the middle reaches of the Heihe River basin. The method proposed is a combination of the daily SEBS results and data collected by meteorological stations. The result shows that the annual ET increased gradually during the period 1990-2004 and the main impact factor on the long-term increase of annual ET was the vegetation change. The accuracy of the ET result is validated using a water balance for the whole watershed and the validation reveals that the SEBS algorithm can be used to effectively estimate annual ET in the Zhangye basin. Chapter 4 establishes the quantitative relationship between the runoff of the Heihe River and the long-term vegetation change of the Ejina oasis, located in the lower reaches of the Heihe River. In this part, two time periods are distinguished corresponding to before and after the implementation of a new water allocation scheme in the Heihe River basin. The GIMMS NDVI and MODIS NDVI data sets are used to quantify the long-term change of the oasis vegetation in the first period 1989-2002 and the second period 2000-2006, respectively. The vegetation change shows a decreasing trend from 1989 to 2002 and an increasing trend between 2000 and 2006. Good relation between the runoff of the river and the vegetation growth are found at both stages and the time lag of the observed hysteresis effect of the runoff of the river on the oasis vegetation is one year. In addition, the yearly smallest water amount which sustains the demand of the eco-environment of the Ejina area is estimated to be 4×108 m3 based on MODIS images. Chapter 5 explores a method to quantify the effect of the groundwater depth on the vegetation growth in the year 2000 in the oasis area by combining MODIS NDVI with groundwater observation data. The result demonstrates that the groundwater depth suitable for vegetation growth in this region ranges from 2.8 to 5 m, depending on species composition. Hardly any vegetation growth occurs when the groundwater depth is below 5 m because the rooting depth of the occurring species is limited and cannot maintain adequate water supplies to their canopies when the water depth is below 5 m. The situation changes after implementation of the new water allocation scheme since 2000. The mean NDVI increased and the annual conversion of bare land into vegetated land is about 38 km2 per year during the period 2000 – 2008. It reflects a potential recovery of the eco-environment of the Ejina area. Chapter 6 comprises the main conclusions and the outlook for possible improvements in future research. The main contribution of this study is the successful integration of remote sensing with ecohydrology in quantifying the relationship between water resources and vegetation occurrence at large scale. It provides a methodology to evaluate the long-term vegetation change and the water resources impact using remote sensing data in water-limited areas. The approach of vegetation dynamics, runoff and groundwater impacts presented in this thesis serves as a sound foundation for predicting the effects of future environmental changes. <br/

The role of aerodynamic resistance in thermal remote sensing-based evapotranspiration models

Aerodynamic resistance (hereafter ra) is a preeminent variable in evapotranspiration (ET) modelling. The accurate quantification of ra plays a pivotal role in determining the performance and consistency of thermal remote sensing-based surface energy balance (SEB) models for estimating ET at local to regional scales. Atmospheric stability links ra with land surface temperature (LST) and the representation of their interactions in the SEB models determines the accuracy of ET estimates. The present study investigates the influence of ra and its relation to LST uncertainties on the performance of three structurally different SEB models. It used data from nine Australian OzFlux eddy covariance sites of contrasting aridity in conjunction with MODIS Terra and Aqua LST and leaf area index (LAI) products. Simulations of the sensible heat flux (H) and the latent heat flux (LE, the energy equivalent of ET in W/m2) from the SPARSE (Soil Plant Atmosphere and Remote Sensing Evapotranspiration), SEBS (Surface Energy Balance System) and STIC (Surface Temperature Initiated Closure) models forced with MODIS LST, LAI, and in-situ meteorological datasets were evaluated against flux observations in water-limited (arid and semi-arid) and energy-limited (mesic) ecosystems from 2011 to 2019. Our results revealed an overestimation tendency of instantaneous LE by all three models in the water-limited shrubland, woodland and grassland ecosystems by up to 50% on average, which was caused by an underestimation of H. Overestimation of LE was associated with discrepancies in ra retrievals under conditions of high atmospheric instability, during which uncertainties in LST (expressed as the difference between MODIS LST and in-situ LST) apparently played a minor role. On the other hand, a positive difference in LST coincided with low ra (high wind speeds) and caused a slight underestimation of LE at the water-limited sites. The impact of ra on the LE residual error was found to be of the same magnitude as the influence of LST uncertainties in the semi-arid ecosystems as indicated by variable importance in projection (VIP) coefficients from partial least squares regression above unity. In contrast, our results for the mesic forest ecosystems indicated minor dependency on ra for modelling LE (VIP \u3c 0.4), which was due to a higher roughness length and lower LST resulting in the dominance of mechanically generated turbulence, thereby diminishing the importance of buoyancy production for the determination of ra

Estimation of Evapotranspiration Over Harran Plain Using Sebs Model

Thesis (M.Sc.) -- İstanbul Technical University, Eurasia Institute of Earth Sciences, Yüksek LisansTez (eng) -- İstanbul Teknik Üniversitesi, Avrasya Yer Bilimleri Enstitüsü, Yüksek LisansIn recent years, human activity and climate change greatly threaten water resources. Evapotranspiration (ET) is one of the most important components in the water cycle. Estimation of evapotranspiration has always been faced with many uncertainties. Estimating evaporation based on physical and experimental equations is very common. These methods are based on meteorological data whose shortcomings limit the use of these relations. For instance, this information is point-specific and related to meteorological stations. Another uncertainty problem is regional estimation by using statistical methods. Over the past few decades, many studies have been carried out on estimating evapotranspiration using remote sensing technology. One of the methods which are widely used for estimating ET is SEBS algorithm. The SEBS was proposed for estimating fluxes of heat or energy and estimating evaporation fraction [24]. This study aims to estimate ET over the Harran Plain that has the largest agricultural irrigation systems in the Southern Anatolian Project. Evapotranspiration is estimated for 2015. Cloud-free days in each season of 2015 are selected. Results compared with data obtained from TARBIL and evapotranspiration extracted from GLDAS products. TARBIL project gives reference evapotranspiration. For calculating the actual ET from the TARBIL data crop coefficient (Kc) was required. The assumption for estimating Kc is based on cotton plants. Kc for this study considered from 0.35 to 1.3. SEBS shows very good compatibility results with TARBIL data with a 10% error but ET extracted from GLDAS was not in the expected range (0 to 2.7 mm/day). GLDAS generates ET in 0.25-degree (27.5×27.5 km) resolution that it is not enough for relatively small areas like Harran plain while SEBS estimates ET in high resolution (1×1 km). For studies of water management, water budget, land surface fluxes in the area with low vegetation cover and also in large scales GLDAS can be used but in case of our target that it is the estimation of ET in agricultural lands especially in a relatively small area SEBS gives us more accurate and more trustworthy ET.Son yıllarda, insan etkinliği ve iklim değişikliği su kaynaklarını büyük ölçüde tehdit etmektedir. Terleme ve buharlaşma su döngüsünde en önemli bileşenlerdendir. Evapotranspirasyon (ET) hesaplanması esnasında her zaman belirsizlikler yaşanmıştır. Fiziksel ve deneysel eşitliklere dayalı buharlaşma tahmini oldukça yaygındır. Bu yöntemler meteorolojik verilere dayanmaktadır. Verilerde yer alan eksiklikler bu ilişkinin kurulmasını zorlaştırmaktadır. Örneğin, bir meteoroloji istasyonundan alınan bir veri sadece o noktaya özgüdür. Bir diğer belirsizlik yaşanan alan da istatistiksel yöntemler kullanılarak yapılan bölgesel tahminlerdir. Son zamanlarda, uzaktan algılama teknolojisini kullanarak terleme ve buharlaşmanın tahmini konusunda birçok çalışma yapılmıştır. ET tahmini esnasında yaygın olarak kullanılan yöntemlerden biri SEBS algoritmasıdır [24]. SEBS, ısı veya enerji akılarının hesaplanması ve buharlaşma tahmini için önerilmektedir. Bu çalışmada, Güney Doğu Anadolu Projesinde (GAP) en büyük tarımsal sulama sistemine sahip olan Harran Ovası'ndaki ET değerinin SEBS ile hesaplanması amaçlanmaktadır. 2015 yılı için tüm mevsimlerdeki bulutsuz günler seçilerek ET hesaplanmıştır. TARBIL ve GLDAS ürünlerinden elde edilen ET verileri, hesaplanan evapotranspirasyon ile karşılaştırıldı. TARBIL verisinden aktüel ET hesaplamak için ürün katsayısı (Kc) gerekmektedir. Kc'nin hesaplanması pamuk bitkilerine göre yapılmıştır dayanmaktadır. Bu çalışma için Kc 0.35 ile 1.3 arasında kabul edildi. SEBS, TARBIL verileriyle oldukça iyi (%10 hatayla) uyumluluk sonuçları göstermektedir, ancak GLDAS'tan üretilen daha uyumsuzdur. GLDAS, 0.25 derece çözünürlükte ET üretmektedir ve bu çözünürlük Harran ovası gibi görece küçük alanları yeteri kadar iyi çözememektedir. SEBS ise ET'yi daha yüksek çözünürlükte tahmin etmektedir. Su yönetimi çalışmalarında, su bütçesi hesaplamalarında, bitki örtüsünün düşük olduğu bölgelerde, ve aynı zamanda büyük alanlardaki toprak yüzeyinde akışların takibi gibi konularda GLDAS kullanılabilmektedir, ancak bu çalışmadakine benzer görece küçük alanlarda bulunan tarım arazilerinin ET tahmininde SEBS bize daha güvenilir ve doğru sonuç vermektedir.M.Sc.Yüksek Lisan

Evaluating the potential of using satellite earth observation data to quantify the contribution of riparian total evaporation to streamflow transmission losses.

Doctor of Philosophy in Hydrology. University of KwaZulu-Natal. Pietermaritzburg, 2017.Numerous perennial rivers which flow through arid and semi-arid environments in South Africa, have become severely constrained as water resources abstractions are close to exceeding, or have exceeded the available supply and ecosystem resilience. This is a common phenomenon, as river basins are increasingly developed and often over allocated, in order to maximize socio-economic benefits through consumptive water use, often at the expense of the environment. Thus, managing and maintaining environmental water requirement (EWR) flow allocations in these circumstances becomes increasingly important but all the more challenging, especially during periods of water scarcity. The Letaba River situated in the semi-arid north-eastern region of South Africa is a typical example of a river system in which water governance challenges and infrastructural development have resulted in flows within the river no longer resembling the natural flow regime. This situation has improved to some extent after the establishment of river operating rules and an adaptive operational water resources management system. However, one of the major challenges with successfully implementing and managing EWR flows to date has been the uncertainty regarding the magnitude and influence of streamflow transmission losses (TL’s) on flows within the river system. TL’s along the Letaba are thought to be a significant proportion of streamflow during dry periods and this therefore constrains the ability to meet target EWR flows, as it is often the case that specified EWR releases from the Tzaneen dam are not adequately met further downstream at EWR target gauges. To ensure that water provisions and in particular EWR flows can be managed more effectively and efficiently in the future, it is imperative that the hydrological processes contributing to TL’s are quantified at various spatial and temporal scales. Considering this statement as a point of departure, the overall objective of this thesis was to reduce the uncertainty associated with TL’s by attempting to acquire an improved hydrological process understanding of the natural drivers of loss in this system, so that TL’s along the Letaba River can be more accurately quantified. This research involved, conducting detailed characterizations of hydrological processes along a 14 km reach of the Groot Letaba River which has similar land use activities and hydrological characteristics to the broader river system. Particular emphasis was placed upon establishing the influence of riparian total evaporation (inclusive of open water evaporation) on TL’s, as this process is a major contributing factor to the water balance of arid and semi-arid environments, yet has seldom been incorporated or adequately represented into TL’s estimation procedures. These investigations were centred on evaluating the potential of using a satellite-based approach to acquire spatially explicit estimates of evapotranspiration (ET) during the low flow period in this river system (May to October), which typically represents a critical period with regards to water shortages. For this purpose, the satellite-based surface energy balance (SEBS) model and satellite earth observation data acquired from Landsat and Moderate-resolution imaging spectroradiometer (MODIS) were used to estimate ET. However, the trade-off between the spatial and temporal resolution associated with these data sets can limit the reliability of satellite-based ET modelling (except where occasionally correct). Consequently, the SEBS ET estimates from these data sets were used as inputs to two relatively simplistic approaches (actual crop coefficient or Kcact and output downscaling with linear regression or ODLR) to quantify ET at a moderate spatial resolution (30 m) on a daily time step. These ET estimates were compared against in-situ ET estimates using a one sensor Eddy Covariance system to quantify any uncertainties associated with the satellite-derived estimates. To further investigate spatial and seasonal variations in source contributions to plant water uptake during the investigation period, stable isotope analysis (of 18O and 2H) and a Bayesian mixing model were coupled with the satellite derived ET estimates. The insights acquired from these investigations, were then used to derive baseline estimates of TL’s. This involved using the satellite-derived daily ET time series in conjunction with data obtained from a parallel investigation focusing on quantifying the rapport between surface and sub-surface water storage processes. Initial comparisons of ET estimates acquired using the Kcact and ODLR approaches against ECET were fairly poor yielding RMSE values of; 1.88 and 2.57 mm d-1 and 1.10 and 2.39 mm d-1 (for two replicate transects), respectively. The poor performance of these techniques was largely attributed to the SEBS ET estimates used as inputs to these techniques, as SEBS may overestimate evapotranspiration during conditions of water stress. This limitation was overcome using an evaporative calibration factor (termed the environmental stress factor or ESF) into the original SEBS formulation (SEBS0), to correct for the overestimation of the latent heat flux (LE) and the evaporative fraction (EF). The ESF calibration factor was empirically derived and then integrated into SEBS0, so as to better represent the influence of water stress on the EF and consequently LE. The implementation of the modified version of SEBS (SEBSESF) was shown to significantly improve the estimation of energy fluxes, which in turn resulted in an improved correlation and an increase in the percentage of modelled ET estimates within an acceptable accuracy range (± 15 to 30 %) when compared against in-situ observations. Through the application of this modified version of SEBS (SEBSESF), the ability of the ODLR and Kcact approaches to develop a time-series of daily moderate spatial resolution ET estimates could now be demonstrated. The use of SEBSESF ET estimates as inputs to the Kcact approach was shown to compare most favourably to ECET, yielding correlation coefficient and Nash-Sutcliffe efficiency values of 0.79 and 0.60, respectively. With the ability of this satellite-based approach to adequately represent ET within this environment now confirmed. Stable isotope analysis (of 18O and 2H) and a Bayesian mixing model were coupled with the Kcact derived ET estimates, to further investigate spatial and seasonal variations in plant water uptake dynamics. The results of these investigations showed that soil water was the main contributing source to ET. While stream and groundwater use during transpiration was also prevalent within the study area and increased with aridity, the magnitude of the contribution of these sources to transpiration was fairly minimal and not as significant as generally reported in literature. The insights gained from these investigations, as well as those obtained from the quantification of surface and sub-surface water storage processes, assisted in deriving baseline estimates of TL’s along the length of river reach studied. In general, it was found that during the latter stages of the dry season (August to October) TL’s accounted for approximately 5 to 15 % of the flow in the river system, with riparian total evaporation and in particular transpiration the dominant contributing processes to this loss. Through linkages with the recent gazetting of the Letaba Management Class (resource objective setting) and the mandatory implementation of EWR flows, it was shown that flows within the river system were unable to meet low flow targets and are required to be increased in order to fulfil this requirement, whilst simultaneously accounting for TL’s. It should be noted that while the various investigations undertaken in this study enabled the estimation of TL’s and the contribution of processes viz. riparian ET to TL’s, the estimates provided could not be verified due to the lack of reliable upstream (inflow) flow gauge data. Although the investigations and observations detailed in this study provide an understanding of the system for a limited period in time, they would substantially benefit from longer-term monitoring, so that the assumptions and related uncertainties that had to be factored into the analysis could be reduced. Overall the study has detailed key hydrological processes influencing TL’s along the Groot Letaba River, providing invaluable insights on existing knowledge gaps and contributing new knowledge to this research area. It is envisaged that this will enable the establishment of an improved conceptual understanding of the system, which may prove to be beneficial for future hydrological modelling applications in this region

Evaluating the influence of the land surface and air temperature gradient on terrestrial flux estimates derived using satellite earth observation data.

Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.Abstract available in pdf