Your search found 18 records
1 Anputhas, Markandu; Ariyaratne, B. Ranjith; Gamage, Nilantha; Jayakody, Priyantha; Jinapala, Kiribandage; Somaratne, Pallewatte G.; Weligamage, Parakrama; Weragala, Neelanga; Wijerathna, Deeptha. 2005. Bringing Hambantota back to normal: a post-tsunami livelihoods needs assessment of Hambantota District in southern Sri Lanka. Colombo, Sri Lanka: International Water Management Institute (IWMI). ix, 59p.
Natural disasters ; Research methods ; Mapping ; Villages ; Income generation ; Statistics ; Irrigated farming ; Livestock ; Fisheries ; Economic aspects ; Rehabilitation / Sri Lanka / Hambantota
(Location: IWMI-HQ Call no: IWMI 363.348068 G744 ANP Record No: H036747)
(2.74 MB)
2 Weragala, Neelanga; Gamage, Nilantha. 2005. Definition of a Tsunami safe boundary for Sri Lanka: a case study in the coastal zone of Galle, Matara and Hambantota Districts. [Abstract only]. Abstract of paper presented at LOICZ II Inaugural Open Science Meeting, Egmond aan zee, Netherlands, 27-29 June 2005. 1p.
(Location: IWMI-HQ Call no: IWMI 353.95 G744 WER Record No: H037592)
(0.11 MB)
3 Thenkabail, Prasad Srinivas; Biradar, Chandrashekhar; Gangodagamage, Chandana; Islam, Aminul; Schull, Mitchell; Gamage, Nilantha; Turral, Hugh; Zomer, Robert; Biggs, Trent; Scott, Christopher; Ahmad, Mobin-ud Din; De Fraiture, Charlotte. 2004. RS/GIS training materials for awareness: version 1.0. Print out of powerpoint presentation made at the Observing river basins from space: why is it important for IWMI - A Remote Sensing and GIS (RS/GIS) Workshop held at the International Water Management Institute, Colombo, Sri Lanka, 28 June 2004. RS/GIS training materials. 6p.
(Location: IWMI-HQ Call no: IWMI 574.526323 G000 IWM Record No: H036216)
4 Smakhtin, Vladimir; Thenkabail, Prasad; Gamage Nilantha. 2006. Developing on-line near-real time drought monitoring system for South West Asia. In Savin, I.; Nègre, T. (Eds.). Agro-meteorological monitoring in Russia and Central Asian countries. Ispra (VA), Italy: Institute for the Protection and Security of the Citizen. pp.104-118.
(Location: IWMI-HQ Call no: IWMI 551.5773 G570 SMA Record No: H039068)
(1.28 MB)
5 Smakhtin, Vladimir; Gamage, Nilantha; Bharati, Luna. 2007. Hydrological and environmental issues of interbasin water transfers in India: a case of the Krishna River Basin. Colombo, Sri Lanka: International Water Management Institute (IWMI). 26p. (IWMI Research Report 120) [doi: https://doi.org/10.3910/2009.120]
River basins ; Water transfer ; Environmental effects ; Dams ; Reservoirs ; Water resources development ; Irrigation requirements ; Case studies / India / Krishna River / Godavari River
(Location: IWMI HQ Call no: IWMI 333.9162 G635 VLA Record No: H040733)
(677 KB)
This study attempts to examine those unique aspects of interbasin water transfer planning, which are of critical importance to the sustainable water resources development in India. It focuses on the crucial aspect of accurate quantification of surface water availability, which determines the entire feasibility of a water transfer. It also illustrates the impacts of upstream water resources development on the deltas' environment thus justifying the deltas' environmental flow requirements. The report targets government departments, research institutions and NGOs - primarily in India and other countries of the region - which are engaged or interested in issues of interbasin water transfer and environmental water management. The research intends to: contribute to the effectiveness of water resources planning and management in India; emphasize the need for urgent improvement of access to hydrometeorological data in the country; and aim to stimulate further debate on water transfers.
6 Ahmad, Mobin-ud-Din; Gamage, Nilantha. 2008. Monitoring agricultural water consumption and irrigation performance using free MODIS images for a large irrigation system in Pakistan. In Humphreys, E.; Bayot, R. S.; van Brakel, M.; Gichuki, F.; Svendsen, M.; Wester, P.; Huber-Lee, A.; Cook, S. Douthwaite, B.; Hoanh, Chu Thai; Johnson, N.; Nguyen-Khoa, Sophie; Vidal, A.; MacIntyre, I.; MacIntyre, R. (Eds.). Fighting poverty through sustainable water use: proceedings of the CGIAR Challenge Program on Water and Food, 2nd International Forum on Water and Food, Addis Ababa, Ethiopia, 10-14 November 2008. Vol.1. Keynotes; Cross-cutting topics. Colombo, Sri Lanka: CGIAR Challenge Program on Water and Food. pp.123-126.
Irrigation systems ; Performance evaluation ; Monitoring ; Water use ; Remote sensing ; Models ; Estimation ; Water stress ; Evapotranspiration ; Mapping ; Groundwater / Pakistan / Indus Basin
(Location: IWMI HQ Call no: IWMI 333.91 G000 HUM Record No: H041786)
http://ifwf2.org/addons/download_presentation.php?fid=1131
https://vlibrary.iwmi.org/pdf/H041786.pdf
https://vlibrary.iwmi.org/pdf/H041786.pdf
7 Smakhtin, Vladimir; Gamage, Nilantha; Bharati, Luna. 2008. Hydrological and environmental issues of inter-basin water transfers in India: a case study of the Krishna River Basin. In Amarasinghe, Upali A.; Sharma, Bharat R. (Eds.) Strategic Analyses of the National River Linking Project (NRLP) of India, Series 2. Proceedings of the Workshop on Analyses of Hydrological, Social and Ecological Issues of the NRLP, New Delhi, India, 9-10 October 2007. Colombo, Sri Lanka: International Water Management Institute (IWMI) pp.79-106.
River basin management ; River basin development ; Development projects ; Water transfer ; Flow ; Water availability ; Surface water ; Water balance ; Environmental effects ; Erosion ; Coasts / India / Krishna River Basin / Pennar Basin / Godavari River Basin
(Location: IWMI HQ Call no: IWMI 333.9162 G635 AMA Record No: H041800)
(310.14 KB)
8 Gamage, Nilantha; Ahmad, Mobin-ud-Din; Muthuwatta, Lal P. 2009. The use of medium resolution remote sensing data to compare spatio-temporal variation of irrigation performances and water consumption. In Anderssen, R. S.; Braddock, R. D.; Newham, L. T. H. (Eds.). Proceedings of the 18th World IMACS Congress and MODSIM09 International Congress on Modelling and Simulation, Cairns, Australia, 13–17 July 2009. Canberra, Australia: Modelling and Simulation Society of Australia and New Zealand; Canberra, Australia: International Association for Mathematics and Computers in Simulation. pp.3697-3703.
Irrigation systems ; Canals ; Groundwater ; Conjunctive use ; Performance indexes ; Water use ; Water stress ; Irrigation management ; Policy making ; Equity ; Evapotranspiration ; Remote sensing ; Models ; Monitoring ; Evaluation / Pakistan / Punjab / Indus Basin
(Location: IWMI HQ Call no: e-copy only Record No: H042278)
(0.43 MB)
Precise information on irrigation performance and water consumption at field or canal command level is important to irrigation managers and policymakers to make appropriate decisions on water management. Use of irrigation performance indices cum water consumption are the tools make such decisions. Calculate those figures are a challenging task for the past cropping years, that essential to make correct decisions especially in data-scarce regions of Asia and Africa. Similarly, calculation of these above at field or canal command level over large irrigation schemes are laborious, costly, timely inefficient and less accurate. The necessity for these figures is rapidly increasing due to the need to make the correct decisions with the continually rising population and food demand cum declining water availability parallel to climatic change issues.
Accordingly, well established surface energy balance algorithm (SEBAL) technique has been employed in large irrigated areas in Punjab, Pakistan, as a tool to estimate actual evapotranspiration (ETa), i.e., water consumption for the cropping years of 2004/05 and 2006/07. Freely available medium resolute daily MODIS images and hydrometeorological data were used as inputs for the ETa calculation. Under this study irrigation performance indices of equity and adequacy were calculated using actual evapotranspiration and evaporative fraction.
Results show that annual ETa varies from less than 100 mm/year in desert/barren areas to 1,650 mm/year over large water bodies. For cropped areas, the variation ranges from 400 to 1,200 mm per year for both cropping years. In rice-wheat area of Punjab, average ETa of the cropping year 2004/05 is 896 mm, and 971 mm for cropping year 2006/07. In lower and southern Punjab, ETa is low and varies from 805 to 870 mm during 2004/05 and 2006/07, respectively. ETa was further analyzed in depth on a seasonal and canal command basis for a better understanding and shows that an average of 9% more water has been consumed by crops during the Kharif 2007 season while 10% higher consumption was observed for the Rabi 2006/07 season than in the previous 2004/05 cropping year. ETa of the Thal Canal has increased by 44% in the Kharif 2007 season followed by Lower Jhelum Canal with 28%. ETa of Upper Jhelum Canal has also increased by about 20% while that of Panjnad Canal has increased by 22% in the Rabi 2006/07 season. Equity of water consumption in 2006/07 has improved considerably compared to 2004/05 in many canals, especially Central Bari Doab, Bahawal, Thal, Chashma Right Bank, Muzaffargarh and Panjnad, which figured as 2, 12, 11, 7, 8 and 8%, respectively. Similarly, adequacy has also improved in many canal commands in the 2006/07 cropping year when compared to 2004/05. This study demonstrates how a remote sensing based estimation of water consumption and water stress can be combined to provide a better estimation of system and irrigation performance at a variety of spatial and temporal scales that would assist water managers and policymakers.
Accordingly, well established surface energy balance algorithm (SEBAL) technique has been employed in large irrigated areas in Punjab, Pakistan, as a tool to estimate actual evapotranspiration (ETa), i.e., water consumption for the cropping years of 2004/05 and 2006/07. Freely available medium resolute daily MODIS images and hydrometeorological data were used as inputs for the ETa calculation. Under this study irrigation performance indices of equity and adequacy were calculated using actual evapotranspiration and evaporative fraction.
Results show that annual ETa varies from less than 100 mm/year in desert/barren areas to 1,650 mm/year over large water bodies. For cropped areas, the variation ranges from 400 to 1,200 mm per year for both cropping years. In rice-wheat area of Punjab, average ETa of the cropping year 2004/05 is 896 mm, and 971 mm for cropping year 2006/07. In lower and southern Punjab, ETa is low and varies from 805 to 870 mm during 2004/05 and 2006/07, respectively. ETa was further analyzed in depth on a seasonal and canal command basis for a better understanding and shows that an average of 9% more water has been consumed by crops during the Kharif 2007 season while 10% higher consumption was observed for the Rabi 2006/07 season than in the previous 2004/05 cropping year. ETa of the Thal Canal has increased by 44% in the Kharif 2007 season followed by Lower Jhelum Canal with 28%. ETa of Upper Jhelum Canal has also increased by about 20% while that of Panjnad Canal has increased by 22% in the Rabi 2006/07 season. Equity of water consumption in 2006/07 has improved considerably compared to 2004/05 in many canals, especially Central Bari Doab, Bahawal, Thal, Chashma Right Bank, Muzaffargarh and Panjnad, which figured as 2, 12, 11, 7, 8 and 8%, respectively. Similarly, adequacy has also improved in many canal commands in the 2006/07 cropping year when compared to 2004/05. This study demonstrates how a remote sensing based estimation of water consumption and water stress can be combined to provide a better estimation of system and irrigation performance at a variety of spatial and temporal scales that would assist water managers and policymakers.
9 Eriyagama, Nishadi; Smakhtin, Vladimir; Gamage, Nilantha. 2009. Mapping drought patterns and impacts: a global perspective. Colombo, Sri Lanka: International Water Management Institute (IWMI). 23p. (IWMI Research Report 133) [doi: https://doi.org/10.3910/2009.132]
Drought ; Impact assessment ; Indicators ; Hydrology ; Mapping ; Climate change ; River basins ; Dams ; Water scarcity ; Disasters ; Risks ; Precipitation ; Runoff ; Soil degradation
(Location: IWMI HQ Call no: IWMI 551.523 G000 ERI Record No: H042368)
(1.40MB)
The study examines the global pattern and impacts of droughts through mapping several drought-related characteristics - either at a country level or at regular grid scales. It appears that arid and semi-arid areas also tend to have a higher probability of drought occurrence. It is illustrated that the African continent is lagging behind the rest of the world on many indicators related to drought-preparedness and that agricultural economies, overall, are much more vulnerable to adverse societal impacts of meteorological droughts. The study also examines the ability of various countries to satisfy their water needs during droughts using storage-related indices.
10 Gamage, Nilantha; Ahmad, Mobin ud Din; Turral, H. 2009. Mapping irrigated crops from Landsat ETM + imagery for heterogeneous cropping systems in Pakistan. In Thenkabail, P. S.; Lyon, J. G.; Turral, H.; Biradar, C. M. (Eds.). Remote sensing of global croplands for food security. Boca Raton, FL, USA: CRC Press. pp.421-437. (Taylor & Francis Series in Remote Sensing Applications)
(Location: IWMI HQ Call no: 631.7.1 G000 THE Record No: H042433)
(0.64 MB)
11 Eriyagama, Nishadi; Smakhtin, Vladimir; Gamage, Nilantha. 2010. A global picture of drought occurrence, magnitude and preparedness. Paper presented at the Second International Drought Conference on Economics of Drought and Drought Preparedness in a Climate Change Context, Istanbul, Turkey, 4-6 March 2010. 9p.
(Location: IWMI HQ Call no: e-copy only Record No: H042774)
(2.20 MB)
This study examines the global patterns and impacts of droughts through the mapping of several drought-related characteristics – either at a grid or a country scale. Characteristics cover various aspects of droughts from global distribution of meteorological and hydrological drought risks to social vulnerability and indices related to water infrastructure. The maps are produced by integrating a number of publicly available global datasets. The subsequent discussion of maps allows a number of policy relevant messages to be extracted. It appears that arid and semi-arid areas also tend to have a higher probability of drought occurrence. In drought years, the highest per capita loss of river flow occurs in areas that do not normally experience climate–driven water scarcity. The study illustrates that the African continent is lagging behind the rest of the world on many indicators related to drought preparedness and that agricultural economies, overall, are much more vulnerable to adverse societal impacts of meteorological droughts. Also highlighted are regions having the largest drought deficits and durations. The ability of various countries to satisfy their water needs during drought conditions is examined using storage-related indices.
12 Gamage, Nilantha; Smakhtin, Vladimir. 2009. Do river deltas in east India retreat?: a case of the Krishna Delta. Geomorphology, 103(4):533-540. [doi: https://doi.org/10.1016/j.geomorph.2008.07.022]
Erosion ; Coastal area ; Environmental effects ; Reservoirs ; Sedimentation ; Case studies ; Deltas / India / Krishna River Basin / Godavari River Basin
(Location: IWMI HQ Call no: e-copy only Record No: H042785)
(1.15 MB)
The construction of multiple dams and barrages in many Indian River basins over the last few decades significantly reduced river flow to the sea and affected the sediment regime. More reservoir construction is planned through the proposed National River Linking Project (NRLP), which will transfer massive amounts of water from the North to the South of India. The impacts of these developments on fertile and ecologically sensitive deltaic environments are poorly understood and quantified at present. In this paper an attempt is made to identify, locate and quantify coastal erosion and deposition processes in one of the major river basins in India—the Krishna—using a time series of Landsat images for 1977, 1990 and 2001 with a spatial resolution ranging from 57.0 m to 28.5 m. The dynamics of these processes are analyzed together with the time series of river flow, sediment discharge and sediment storage in the basin. Comparisons are made with similar processes identified and quantified earlier in the delta of a neighboring similarly large river basin—the Godavari. The results suggest that coastal erosion in the Krishna Delta progressed over the last 25 years at the average rate of 77.6 ha yr- 1, dominating the entire delta coastline and exceeding the deposition rate threefold. The retreat of the Krishna Delta may be explained primarily by the reduced river inflow to the delta (which is three times less at present than 50 years ago) and the associated reduction of sediment load. Both are invariably related to upstream reservoir storage development.
13 Kirby, M.; Mainuddin, M.; Ahmad, Mobin-ud-Din; Gamage, Nilantha; Thomas, M.; Eastham, J. 2010. Water-use accounts in CPWF basins: simple water-use accounting of the Karkheh Basin. Colombo, Sri Lanka: CGIAR Challenge Program on Water and Food (CPWF). 21p. (CPWF Working Paper: Basin Focal Project Series BFP008)
(Location: IWMI HQ Call no: e-copy only Record No: H042846)
https://cgspace.cgiar.org/bitstream/handle/10568/12537/CPWF_BFP_WP_08.pdf?sequence=1
https://vlibrary.iwmi.org/pdf/H042846.pdf
https://vlibrary.iwmi.org/pdf/H042846.pdf
(0.66 MB) (676 KB)
This paper applies the principles of water-use accounts, developed in the first of the series, to the Karkheh River basin in Iran. The Karkheh Basin lies primarily in Iran with its extreme downstream discharge into the Hawr Al Azim marshes on the border with Iraq. The northern part of the Basin where the Karkheh and its tributaries rise is mountainous, cooler, and wetter. The River spills out on to the hotter, lower semi-arid plains at its southern end. Near the downstream end of the Karkheh River is a major dam, built recently to supply water for irrigation. Precipitation, mainly in winter, varies from 400-500 mm in the upper part of the Basin falling to about 230 mm in the lower reaches. Rainfall exceeds evaporation only for a few winter months, and only in the upper catchment. Preciptiation varies considerably from year to year. Net runoff from the basin is less than 2% of total precipitation. Total water use exceeds rainfall by about 14%, the difference is assumed to be largely pumped groundwater in the upper and middle parts of the basin. Grassland is the most extensive land use and uses about 50% of the total available water. Irrigation, although occupying a smaller area, consumes about 28% of the available water followed by rainfed agriculture, which consumes about 20%. Plausible figures for the effect of the Karkheh Dam suggest that it will reduce flows downstream of the Dam and the inflow into the Hawr Al Azim marshes.
14 Jayakody, Priyantha; Gamage, Nilantha. 2010. Surface runoff estimation over heterogeneous canal commands applying medium resolution remote sensing data with the SCS-CN method. In Weligamage, Parakrama; Godaliyadda, G. G. A.; Jinapala, K. (Eds.). Proceedings of the National Conference on Water, Food Security and Climate Change in Sri Lanka, BMICH, Colombo, Sri Lanka, 9- 11 June 2009. Vol. 1. Irrigation for food security. Colombo, Sri Lanka: International Water Management Institute (IWMI). pp.143-152.
(Location: IWMI HQ Call no: IWMI 631.7 G744 WEL Record No: H042900)
The precise estimation of surface runoff from rainfall is critical for water resource management. In the recent past, remote sensing and Geographic Information System (GIS) technologies have been widely used in the estimation of surface runoff from watersheds, and from agricultural fields in particular. This is due to the inherent ability of remote sensing to capture spatial heterogeneity of surface parameters such as land use and land cover. This could lead to better performances of surface runoff simulation models. Surface runoff volume/rate estimation involves quantifying the amount of rainfall exceeding infiltration and initial abstractions which must be satisfied before the occurrence of runoff. The widely accepted SCS curve number method was employed to calculate surface runoff, using a combination of remotely-sensed land use/land cover and hydrometrological data in the Punjab canal command areas. Land use/Land cover maps for four cropping seasons, Rabi 2004-05, Kharif 2005, Rabi 2006-07 and Kharif 2007 were derived using red and near infrared bands of MODIS 8 day products. The existing soil map was reclassified into hydrological soil groups and rainfall data were interpolated using the inverse distance method to represent the spatial rainfall values of each canal command. The results show that CN values vary from 70 to 95 during the study period. The highest CN value of 94.4 is during the Kharif 2005 season. Meanwhile the runoff-coefficient is changing from 0.01 to 0.25 and 0.01 to 0.43, respectively, during Rabi 2004/05 and Rabi 2006/07. During Kharif 2005 and Kharif 2007, the runoff-coefficient varied from 0.01 to 43 and 0.01 to 0.45, respectively. The study shows that the SCS curve number method can be used for runoff estimation with the help of remote sensing products and GIS technologies from catchments where gauging data is not available.
15 Bharati, Luna; Gamage, Nilantha. 2010. Application of the Pitman Model to generate discharges for the Lhasa Basin, China. Hydro Nepal: Journal of Water, Energy and Environment, 7:30-34.
River basin management ; Rainfall-runoff relationships ; Simulation models ; Hydrology ; Stream flow / China / Tibet / Nepal / Lhasa River Basin / Koshi River Basin
(Location: IWMI HQ Record No: H043101)
http://www.nepjol.info/index.php/HN/article/download/4233/3593
https://vlibrary.iwmi.org/pdf/H043101.pdf
https://vlibrary.iwmi.org/pdf/H043101.pdf
(4.49 MB) (609KB)
Predicting river flows in basins where limited data is available is a challenge facing many hydrologists especially in developing countries. In this study, the Pitman monthly model was applied to generate flows for the Lhasa Basin in China (Tibet). As flow data was unavailable for the Lhasa basin, the model was first calibrated for the upper Koshi Basin in Nepal and China. The Pitman model successfully predicted flows for the upper Koshi basin (R2=0.88). Therefore, the estimated model parameters from the Koshi basin as well as climate data from the Lhasa basin were used to generate flows for the Lhasa basin outlet. The main modeling assumption is that the basin characteristics of the upper Koshi are similar to that of the Lhasa basin. Under present circumstances, where measured data is unavailable, the model estimated monthly flows for the Lhasa basin can be used in further studies in basin water accounting and management.
16 Gamage, Nilantha; Agrawal, R.; Smakhtin, Vladimir; Perera, B. J. C. 2011. An artificial neural network model for simulating streamflow using remote sensing data. In International Association for Hydro-Environment Engineering and Research (IAHR); Engineers Australia (EA). National Committee on Water Engineering (NCWE). 34th IAHR World Congress, Balance and Uncertainty: Water in a Changing World, Brisbane, Australia, 26 June - 1 July 2011. Brisbane, Australia: International Association for Hydro-Environment Engineering and Research (IAHR); Brisbane, Australia: Engineers Australia (EA). National Committee on Water Engineering (NCWE). pp.1371-1378.
Remote sensing ; Stream flow ; Neural networks ; Rain ; Evapotranspiration ; Seasonal variation ; Models ; Catchment areas / Australia / Victoria / Macalister subcatchment
(Location: IWMI HQ Call no: e-copy only Record No: H044002)
(1.11 MB)
Streamflow data play a key role in water resources management; however these data are not often available. One of the alternatives then is to use the rainfall-runoff models, but in most cases the required inputs such as rainfall and evapotranspiration are not available to use these models. Freely available remote sensing data, which represent features of the above input variables, can be used to generate streamflow data as an alternative. This project uses daily Moderate Resolution Imaging Spectrometer (MODIS) data to generate daily streamflow for the Thomson catchment in Victoria in Australia through an Artificial Neural Network (ANN) model. Daily MODIS reflectance and radiance data were first converted to Normalized Difference Vegetation Index (NDVI) and cloud top temperature (CTT) respectively. Several ANN models with one hidden layer were then developed using combinations of present day NDVI and CTT variables, and several daily lags of these variables. Results showed that a seasonally stratified model with five inputs had given predictions comparable to observed streamflow. Five inputs were present day NDVI and CTT, and three past days of CTT.
17 Gamage, Nilantha; Smakhtin, Vladimir; Perera, B. J. C. 2011. Estimation of actual evapotranspiration using remote sensing data. In Chan, F.; Marinova, D.; Anderssen, R. S. (Eds.). MODSIM 2011, 19th International Congress on Modelling and Simulation - Sustaining Our Future: Understanding and Living with Uncertainty, Perth, Australia, 12-16 December 2011. Canberra, Australia: Modelling and Simulation Society of Australia and New Zealand. pp.3356-3362.
Remote sensing ; Evapotranspiration ; Precipitation ; Vegetation ; Catchment areas ; Hydrology / Australia / Victoria / Thomson Catchment / Macalister Sub Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H044660)
(1.49 MB)
Estimation of actual evapotranspiration (AET) and its spatial distribution are important to understanding of catchment hydrology. The AET is driven by net energy available to evaporate water from soil and vegetation surfaces, and to transpirate water from vegetation. However, estimating AET is difficult as the evapotranspiration process involves complex physical and biological processes. It is further complicated when there is lack of measured meteorological variables data which are required for estimation. These data are essential to quantify the availability of net energy and the aerodynamic effects of the evapotranspiration process. Remote sensing (RS) data, which are widely available and easily accessible than the measured ground data, can be used to estimate the availability of net energy for AET. However, still some measured ground data are required to quantify the aerodynamic effects on AET. In this study, remote sensing data and readily available climate datasets were used as inputs to an energy balance technique to estimate AET, as an alternative to the traditional ET estimation procedures, which require measured hydrometeorological data. The Macalister subcatchment in the Thomson catchment in Victoria (Australia) was used as the case study considering the study period from January 2003 to December 2008.Reflectance and radiance data of Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra satellite were the primary source of RS data. Tilted and absent images of Terra MODIS were replaced with Aqua satellite data. First, vegetation indices such as Normalized Difference Vegetation Index, Leaf Area Index, fractional vegetation coverage and broadband albedo were calculated based on MODIS reflectance data for non-cloudy days. Similarly, MODIS radiance data were used to generate daily surface temperature on non-cloudy days. Vegetation indices and surface temperature were then used in the Surface Energy Balance System (SEBS) to estimate AET for non-cloudy days. However, SEBS requires data on a limited number of meteorological variables to quantify the aerodynamic effect of AET, and those data were obtained from ground measurements and global climate datasets (i.e. IWMI climate and water atlas). Once the AET was estimated for non-cloudy days, eostationary Operational Environmental Satellite (GOES) data were used to calculate fractional cloud cover and used to estimate net radiation available for cloudy day AET. The accuracy of the non-cloudy and cloudy day AET estimated using RS data was studied using root mean square error (RMSE) and Nash-Sutcliffe efficiency (Ef), by considering Penman-Monteith (PM) based AET as the observed AET, at four different sites in the atchment. A crop coefficient was used to convert PM based reference crop evapotranspiration to PM based AET. Remote sensing based AET shows higher coefficient of determination (R2) compared to PM based AET on non-cloudy days and comparatively less R2 on cloudy days. Results revealed that RS based AET overestimated during non-cloudy days, especially when the AET is more than 3 mm/day. However, RS based AET underestimated during partial and total cloud days. The above observations are common to all selected sites. Similar observations were seen with RMSE and Ef at all sites. The results show that remote sensing data and global climate dataset can be successfully used to estimate AET for the catchments where required ground measured meteorological data are not available. The estimated AET can be used as input to streamflow simulation models to generate streamflow in data poor catchments.
18 Smakhtin, Vladimir; Thenkabail, Prasad; Gamage, Nilantha; Weragala, Neelanga. 2005. Drought assessment and monitoring in South Asia using climate and remote sensing data. In Mathur, G. N.; Chawla, A. S. (Eds.). Water for sustainable development - towards innovative solutions: proceedings of the XII World Water Congress, New Delhi, India, 22-25 November 2005. Vol. 3. New Delhi, India: Central Board of Irrigation and Power; Montpellier, France: International Water Resources Association (IWRA). pp.6:97-6:110.
Drought ; Rain ; Assessment ; Monitoring ; Risks ; Indicators ; Remote sensing ; Data ; Indicators / South Asia
(Location: IWMI HQ Call no: 333.91 G000 MAT Record No: H045961)
(1.07 MB)
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