Evaluating Landsat 8 evapotranspiration for water use mapping in the Colorado River Basin

AbstractEvapotranspiration (ET) mapping at the Landsat spatial resolution (100m) is essential to fully understand water use and water availability at the field scale. Water use estimates in the Colorado River Basin (CRB), which has diverse ecosystems and complex hydro-climatic regions, will be helpful to water planners and managers. Availability of Landsat 8 images, starting in 2013, provides the opportunity to map ET in the CRB to assess spatial distribution and patterns of water use. The Operational Simplified Surface Energy Balance (SSEBop) model was used with 528 Landsat 8 images to create seamless monthly and annual ET estimates at the inherent 100m thermal band resolution. Annual ET values were summarized by land use/land cover classes. Croplands were the largest consumer of “blue” water while shrublands consumed the most “green” water. Validation using eddy covariance (EC) flux towers and water balance approaches showed good accuracy levels with R2 ranging from 0.74 to 0.95 and the Nash–Sutcliffe model efficiency coefficient ranging from 0.66 to 0.91. The root mean square error (and percent bias) ranged from 0.48mm (13%) to 0.60mm (22%) for daily (days of satellite overpass) ET and from 7.75mm (2%) to 13.04mm (35%) for monthly ET. The spatial and temporal distribution of ET indicates the utility of Landsat 8 for providing important information about ET dynamics across the landscape. Annual crop water use was estimated for five selected irrigation districts in the Lower CRB where annual ET per district ranged between 681mm to 772mm. Annual ET by crop type over the Maricopa Stanfield irrigation district ranged from a low of 384mm for durum wheat to a high of 990mm for alfalfa fields. A rainfall analysis over the five districts suggested that, on average, 69% of the annual ET was met by irrigation. Although the enhanced cloud-masking capability of Landsat 8 based on the cirrus band and utilization of the Fmask algorithm improved the removal of contaminated pixels, the ability to reliably estimate ET over clouded areas remains an important challenge. Overall, the performance of Landsat 8 based ET compared to available EC datasets and water balance estimates for a complex basin such as the CRB demonstrates the potential of using Landsat 8 for annual water use estimation at a national scale. Future efforts will focus on (a) use of consistent methodology across years, (b) integration of multiple sensors to maximize images used, and (c) employing cloud-computing platforms for large scale processing capabilities

NEXUS Gains Talk 11: Integrating Water Resources Management in a Shared River Basin

This webinar discusses application of a nexus tool to support water allocation reform in the Incomati Basin. NEXUS Gains has partnered with INMACOM and the University of Manchester to build a robust and comprehensive river basin systems model using an open-source Python water resources (Pywr) framework that accounts for water demands from agriculture, domestic, industry, and energy sectors. This webinar outlines the process of model co-development and presents preliminary results centering on emerging opportunities to foster greater benefits through more collective basin management

Training Report on Water Accounting

The IWMI WA team and IWMI MENA conducted three days training December 5-7, 2022, for partners in Egypt on the use of the “Water Accounting Plus (WA+)” as part of the CGIAR regional integrated initiative: “From Fragility to Resilience in Central and West Asia and North Africa (#F2RCWANA)”. The aim of the initiative is to respond to the climate, nutrition and agrifood challenges most affecting the CWANA region. The F2R-CWANA Initiative is a 10-year Project implemented by International Water Management Institute (IWMI), ICARDA; International Center for Agricultural Research in the Dry Areas, IFPRI, World Fish, CIMMYT, CIP and ABC. The Initiative has five planned regional anchor countries – Egypt, Lebanon, Morocco, Uzbekistan and Sudan– representing different regional needs and a range of social contexts. The three day training was part of Work package 4 “integrated food, land, water and energy systems for climate-resilient landscapes”. The training was held in Cairo with 14 participants representing Engineers, researchers, ministry agents and Regional water resources and irrigation offices from Egypt, Lebanon, Jordan, Uzbekistan, Syria and Sudan (Annex 1). The training aimed to build partners capacity on the innovation “Water Accounting Plus (WA+)” as a decision-support tool developed by IWMI and its partners IHE, FAO to enhance water resources management, water productivity while reducing trade-offs. The training materials were prepared, and conducted by Dr. Mansoor Leh, Researcher, Dr Naga Velpuri, Senior Researcher and Mr. Prabath Thilina, Software Developer at IWMI which is a global leader in water accounting and water productivity applied and development research

New nexus tool supports holistic management of the Incomati Basin

From its sources in the western mountains and plateau of Mpumalanga in South Africa to its mouth just north of Maputo’s bustling docks in Mozambique, the Incomati River basin supports lives, livelihoods, and irreplaceable ecosystems across eastern Southern Africa. However, growing irrigation and energy needs and accelerating climate change have placed increasing water stress on the transboundary river basin. Without responsive, data-driven, and coordinated management from the basin’s three countries – South Africa, Eswatini, and Mozambique – the lifeblood of the region is at risk of drying up

Operational global actual evapotranspiration: development, evaluation, and dissemination

Satellite-based actual evapotranspiration (ETa) is becoming increasingly reliable and available for various water management and agricultural applications from water budget studies to crop performance monitoring. The Operational Simplified Surface Energy Balance (SSEBop) model is currently used by the US Geological Survey (USGS) Famine Early Warning System Network (FEWS NET) to routinely produce and post multitemporal ETa and ETa anomalies online for drought monitoring and early warning purposes. Implementation of the global SSEBop using the Aqua satellite’s Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature and global gridded weather datasets is presented. Evaluation of the SSEBop ETa data using 12 eddy covariance (EC) flux tower sites over six continents indicated reasonable performance in capturing seasonality with a correlation coefficient up to 0.87. However, the modeled ETa seemed to show regional biases whose natures and magnitudes require a comprehensive investigation using complete water budgets and more quality-controlled EC station datasets. While the absolute magnitude of SSEBop ETa would require a one-time bias correction for use in water budget studies to address local or regional conditions, the ETa anomalies can be used without further modifications for drought monitoring. All ETa products are freely available for download from the USGS FEWS NET website

Evaluating New SMAP Soil Moisture for Drought Monitoring in the Rangelands of the US High Plains

On the Ground • Level 3 soil moisture datasets from the recently launched Soil Moisture Active Passive (SMAP) satellite are evaluated for drought monitoring in rangelands. • Validation of SMAP soil moisture (SSM) with in situ and modeled estimates showed high level of agreement. • SSM showed the highest correlation with surface soil moisture (0-5 cm) and a strong correlation to depths up to 20 cm. • SSM showed a reliable and expected response of capturing seasonal dynamics in relation to precipitation, land surface temperature, and evapotranspiration. • Further evaluation using multi-year SMAP datasets is necessary to quantify the full benefits and limitations for drought monitoring in rangelands.The Rangelands archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform March 202

Spatially Explicit Wastewater Generation and Tracking (SEWAGE-TRACK) in the Middle East and North Africa Region

This study developed the SEWAGE-TRACK model for disaggregating lumped national wastewater generation estimates using population datasets and quantifying rural and urban wastewater generation and fate. The model allocates wastewater into riparian, coastal, and inland components and summarizes the fate of wastewater into productive (direct and indirect reuse) and unproductive components for 19 countries in the Middle East and North Africa (MENA) region. As per the national estimates, 18.4 km3 of municipal wastewater generated in 2015, was disaggregated over the MENA region. Results from this study revealed urban and rural areas to contribute to 79 % and 21 % of municipal wastewater generation respectively. Within the rural context, inland areas generated 61 % of the total wastewater. The riparian and coastal regions produced 27 % and 12 %, respectively. Within the urban settings, riparian areas produced 48 %, while inland and coastal regions generated 34 % and 18 % of the total wastewater, respectively. Results indicate that 46 % of the wastewater is productively used (direct reuse and indirect use), while 54 % is lost unproductively. Of the total wastewater generated, the most direct use was observed in the coastal areas (7 %), the most indirect reuse in the riparian regions (31 %), and the most unproductive losses in inland areas (27 %). The potential of unproductive wastewater as a non-conventional freshwater source was also analyzed. Our results indicate that wastewater is an excellent alternative water source and has high potential to reduce pressure on non-renewable sources for some countries in the MENA region. The motivation of this study is to disaggregate wastewater generation and track wastewater fate using a simple but robust approach that is portable, scalable and repeatable. Similar analysis can be done for other regions to produce information on disaggregated wastewater and its fate. Such information is highly critical for efficient wastewater resource management

Wastewater production, treatment and reuse in MENA: untapped opportunities?

In Mateo-Sagasta, Javier; Al-Hamdi, M.; AbuZeid, K. (Eds.). Water reuse in the Middle East and North Africa: a sourcebook. Colombo, Sri Lanka: International Water Management Institute (IWMI)

Operational Evapotranspiration Mapping Using Remote Sensing and Weather Datasets: A New Parameterization for the SSEB Approach

The increasing availability of multi-scale remotely sensed data and global weather datasets is allowing the estimation of evapotranspiration (ET) at multiple scales. We present a simple but robust method that uses remotely sensed thermal data and model-assimilated weather fields to produce ET for the contiguous United States (CONUS) at monthly and seasonal time scales. The method is based on the Simplified Surface Energy Balance (SSEB) model, which is now parameterized for operational applications, renamed as SSEBop. The innovative aspect of the SSEBop is that it uses predefined boundary conditions that are unique to each pixel for the “hot” and “cold” reference conditions. The SSEBop model was used for computing ET for 12 years (2000-2011) using the MODIS and Global Data Assimilation System (GDAS) data streams. SSEBop ET results compared reasonably well with monthly eddy covariance ET data explaining 64% of the observed variability across diverse ecosystems in the CONUS during 2005. Twelve annual ET anomalies (2000-2011) depicted the spatial extent and severity of the commonly known drought years in the CONUS. More research is required to improve the representation of the predefined boundary conditions in complex terrain at small spatial scales. SSEBop model was found to be a promising approach to conduct water use studies in the CONUS, with a similar opportunity in other parts of the world. The approach can also be applied with other thermal sensors such as Landsat