Forecasting rainfed sorghum yield using satellite-derived vegetation indices with limited ground-based information in Gadarif region, eastern Sudan

A practical crop growth and yield monitoring system based on satellite data is required and fundamental not only for precision farming, but also very useful for global food security enhancement. This study was performed to determine the optimal vegetation index and also to identify the best time for making a reliable crop yield forecast in one of the major sorghum-growing region (Gedarif State, Sudan). The study was also aimed to develop a simple yield prediction model which was later validated using an official yield data acquired during 2013 and 2014 cropping seasons from the Department of Information System and Statistical Analysis of the State Ministry of Agriculture, Gedarif State. The study used NASA’s multi-temporal MODerate resolution Imaging Spectroradiometer (MODIS) land products with limited ground information. Relationship between sorghum yield and crop reflectance indicated that normalized difference vegetation index (NDVI) at the third dekad of September (Sep.III) is the most appropriate to develop sorghum yield prediction model with higher R2 value of 0.77 (p<0.05) compared to other vegetation indices (normalized ratio vegetation index, NRVI and soil-adjusted vegetation index, SAVI). The plotting of estimated yield against actual yield during 2013 and 2014 cropping seasons revealed strong positive and linear correlations (R2 = 0.64 (p=0.06) and 0.74 (p<0.05), respectively with average R2 = 0.71 (p<0.001) for both seasons. This study concluded that a good prediction of rainfed sorghum yield could be achieved more than 30 days before harvesting with quick, accurate and cost-effective method compared to traditional field surveys

Satellite-based energy balance model to estimate seasonal evapotranspiration for irrigated sorghum: a case study from the Gezira scheme, Sudan

The availability of the actual water use from agricultural crops is considered as the key factor for irrigation water management, water resources planning, and water allocation. Traditionally, evapotranspiration (ET) has been calculated in the Gezira scheme as the point of reference with evapotranspiration (ET<sub>o</sub>) and crop coefficients (<i>k</i><sub>c</sub>) being derived from actual measurements of soil-water balance. Recently developed, advanced energy balance models assisted in estimating the ET through the remotely sensed data. In this study Enhanced Thematic Mapper Plus (ETM+) and MODerate Resolution Imaging Spectroradiometer (MODIS) images were used to estimate the spatial distribution of the daily, monthly and seasonal ET for irrigated sorghum in the Gezira scheme, Sudan. The daily ET maps were also used to estimate <i>k</i><sub>c</sub> over time and space. Results of the energy balance, based on being remotely sensed, were compared to actual measurements conducted during 2004/05 season. The seasonal actual ET values, obtained from the seven MODIS images for irrigated sorghum, were estimated at 579 mm. The values for remotely sensed <i>k</i><sub>c</sub>, derived during the initial mid-season and late-season crop development stages, were 0.62, 0.85, 1.15, and 0.48, respectively. On the other hand, the values for the experimental <i>k</i><sub>c</sub> during the pervious mention stages were 0.55, 0.94, 1.21 and 0.65, respectively. The estimated seasonal ET of the sorghum, derived by remotely sensed <i>k</i><sub>c</sub>, was 674 mm. The Landsat data and the Free MODIS provided reliable, exhaustive, and consistent information on the water use, relevant for decision support in the Gezira scheme

Estimation of flooded area in the Bahr El-Jebel basin using remote sensing techniques

International audienceIn spite of the importance of Sudd (swamp) area estimation for any hydrological project in the southern Sudan, yet, no abroad agreement on its size, due to the inaccessibility and civil war. In this study, remote sensing techniques are used to estimate the Bahr El-Jebel flooded area. MODIS-Terra (Moderate Resolution Imaging Spectroradiometer) level 1B satellite images are analyzed on basis of the unsupervised classification method. The annual mean of Bahr El-Jebel flooded area has been estimated at 20 400 km2, which is 96% of Sutcliffe and Park (1999) estimation on basis of water balance model prediction. And only, 53% of SEBAL (Surface Energy Balance Algorithm for Land) model estimation. The accuracy of the classification is 71%. The study also found the swelling and shrinkage pattern of Sudd area throughout the year is following the trends of Lake Victoria outflow patterns. The study has used two evaporation methods (open water evaporation and SEBAL model) to estimate the annual storage volume of Bahr El-Jebel River by using a water balance model. Also the storage changes due time is generated throughout the study years

Satellite-based evapotranspiration and crop coefficient for irrigated sorghum in the Gezira scheme, Sudan

International audienceThe availability of the actual water use from agricultural crops is considered as the key factor for irrigation water management, water resources planning, and water allocation. Traditionally, evapotranspiration (ET) has been estimated in the Gezira scheme by multiplying the reference evapotranspiration (ETo) by crop coefficient (kc) which is derived from the phenomenological crop stages. Recently, advanced developed energy balance models assist to estimate ET through remotely sensed data. In this study Enhanced Thematic Mapper Plus (ETM+) images were used to estimate spatial distribution of daily, monthly and seasonal ET for irrigated sorghum in the Gezira scheme, Sudan. The daily ET maps were also used to estimate kc over time and space. Results of remotely sensed based energy balance were compared with actual measurements conducted during 2004/05 season. The daily actual ET values estimated using the energy balance model during the satellite acquisition dates (28 July, 29 August, 16 October and 17 November) were 4.7, 5.5, 7.1 and 2.7 mm/day, while the average seasonal evapotranspiration for irrigated sorghum estimated to be around 596 mm. The remotely estimated kc values in the initial, crop development, mid-season and late-season stages were 0.62, 0.85, 1.15, and 0.48 respectively. On the other hand the widely used tradition kc values during the pervious mention stages are 0.55, 0.94, 1.21 and 0.65, respectively. This research shows that remotely sensed measurements can help objectively analyzed the irrigation water requirement for different field crops on daily and seasonal time step. Moreover, the remotely sensed real-time data availability provides the system managers with information that not previously available

Performance assessment of the Gash Delta Spate Irrigation System, Sudan

The Gash Delta Spate Irrigation System (GDSIS), located in eastern Sudan with a net command area of 100 000 ha (an area currently equipped with irrigation structures), was established in 1924. The land is irrigated every 3 years (3-year rotation) or every 2 years (2-year rotation) so that about 33 000 or 50 000 ha respectively can be cultivated annually. This study deals with assessing the performance of the 3- and 2-year rotation systems using the Monte Carlo simulation. Reliability, which is a measure of how frequently the irrigation water supply satisfies the demand, and vulnerability, which is a measure of the magnitude of failure, were selected as the performance criteria. Combinations of five levels of intake ratio and five levels of irrigation efficiency for the irrigation water supply of each rotation system were analysed. Historical annual flow data of the Gash River for 107 years were fit to several frequency distributions. The Weibull distribution was the best on the basis of the Akaike information criteria and was used for simulating the ensembles of annual river flow. The reliabilities and vulnerabilities of both rotation systems were evaluated at typical values of intake ratio and irrigation efficiency. The results show that (i) the 3-year rotation is more reliable in water supply than the 2-year rotation, (ii) the vulnerability of the 3-year rotation is lower than that of the 2-year rotation and (iii) therefore the 3-year rotation is preferable in the GDSIS. The sensitivities of reliability and vulnerability to changes in intake ratio and irrigation efficiency were also examined