2011 Annual Report
1a.Objectives (from AD-416)
The objectives are to develop technology to estimate real-time crop coefficients for fields/crops in the San Joaquin Valley from remotely-sensed data and to develop and demonstrate a prototype decision support system that can efficiently deliver crop coefficient and estimated crop water use information to agricultural producers and water suppliers.
1b.Approach (from AD-416)
* Refine and validate the relationship between crop canopy cover (fc) and remotely sensed NDVI. Use ground based multispectral camera to measure fc for a wide range of crops grown in the San Joaquin Valley and compare the fc values with NDVI values derived from both aerial and satellite (Landsat and Modis) multispectral images for the fields.
* Conversion of fc to basal crop coefficient, Kcb. Collect a library of relationships between fc and basal crop coefficient generated from the UC Kearney/ARS peach and grape lysimeters, the ongoing ARS lysimeter studies of vegetable water use at the UC WSREC, and any relationships published in the literature.
* Compare crop water use estimates with this methodology with that predicted by standard (FAO 56) and thermal surface energy balance approaches. Compare predicted ETc based on the proposed methodology (NDVI and localized CIMIS ETo, and estimates of soil evaporation) with estimates of crop water use based on remotely sensed thermal imagery and the Surface Energy Balance approach.
* Develop software and packaging for retrieval and conversion of RS images to geo-rectified Kcb maps. Develop methodology to automatically retrieve appropriate imagery, efficiently calculate NDVI values from the remotely sensed (RS) images, convert the NDVI values to Kcb values, and present the data in a geometrically rectified GIS format that can be efficiently combined with the localized ETo data from CIMIS and other map layers.
* Develop a prototype user interface. Develop a prototype user interface for spatially explicit query (eg, based on geo-coordinates, parcel number, etc) that allows users to efficiently download Kcb and ETo information and efficiently calculate ETc for their fields or districts.
* Feasibility, Costs and Benefits. Estimate the benefits and costs of employing remote sensing technology to improve water use efficiency. Estimate the costs of delivering RS based crop coefficients for the San Joaquin Valley. Estimate the improved irrigation efficiency and water savings that can be expected with this scheduling technology compared to the use of CIMIS ETo data and a traditional crop coefficient approach.
This Reimbursable Agreement supports Objective 1 of the parent project. During this reporting period, an analysis was undertaken to identify an optimal, generic relationship between fraction of cover (fc) and basal crop coefficient (Kcb) that might be used to support broad-area satellite mapping, and to quantify resulting errors in Kcb specification. An FAO-56 interpolation method was used to relate Fc to Kcb for several major annual crop classes using a “density coefficient” based on fc and crop height. The normalized difference vegetation index (NDVI) method was also compared to Surface Energy Balance Algorithm for Land (SEBAL), which derived ET through a surface energy balance approach. Results were presented at the 28th International Horticultural Congress and the 5th National Decennial Irrigation Conference in 2010. Evapotranspiration (ET) techniques based on remotely-sensed data enable efficient estimates of ET over large land areas. Activities of the project are monitored by the lead scientist via email and telephone communications with DWR and project collaborators.