1a. Objectives (from AD-416):
1) Improve current decision making capabilities by building robust data on current practices existing agricultural systems where biomass production could be incorporated (Temple, Parlier, Mandan, Riverside); 2) Create management plans to optimize yield and stability of feedstock production (Temple, Palier, Mandan; 3) Optimize biomass stability and yield while minimizing environmental impacts at greater than field scales (Temple, Parlier, Mandan); and 4) Improve water and air resource management and optimize biomass production for other production areas in the Hawaiian Islands, Pacific Basin, and western United States (Temple, Parlier, Mandan, Hilo).
1b. Approach (from AD-416):
Objective 1: Develop spatial and temporal data sets from historic data for baseline analyses. Objective 2: Simulate current management impacts on feedstock yields and resource inputs. Objective 3: Demonstrate applicability of simulation approaches with validated present practices and explore watershed scale impacts of changes. Objective 4: Improve decision support for assessment of resource conditions, and utilize parallel computing and deep hydrology water balance as needed.
3. Progress Report:
The Navy's dependence on oil (petroleum) strains operational planning. Its focus is on securing a sustainable fuel supply. ARS research and models will help determine best management of natural resources to allow Office of Naval Research (ONR) sustainability in fuel supply while also promoting ecological services and the local economy in Hawaii. Water is the critical resource in biofuel production in Maui. The SWAT model was utilized in this project to simulate the impact of water management and climate on biofuel production. In cooperation with Texas A&M AgriLife Research scientists, SWAT input files for more than 700 integrated management units (sugarcane fields) were updated using current data for elevation, land use, soils, stream network, canal network, dams/reservoirs, precipitation, and temperature. Evapotranspiration algorithms were refined and compared to evapotranspiration estimates from eddy covariance flux towers located in two sugarcane fields. Sugarcane yields during a 10-year period were compared to measured yields at each of the 700 fieldsshowing good agreement between measured and predicted yields. Web-based software was developed to allow users to remotely run the model, update daily precipitation and irrigation, and automatically map irrigation scheduling requirements on the web. The interface is operational on servers in Texas and is being transferred to Hawaiian Commercial and Sugar Company (HC&S) servers for continued support and maintenance. The web–based SWAT tool provides HC&S with a simple, real-time interface for irrigation scheduling decisions. Since water is a critical resource for all biofuel production, with modification, this tool will be applicable to biofuel production in other areas of the U.S. Efficient water management in sugarcane production requires an understanding of water losses. In cooperation with scientists at Baylor University and Texas AgriLife Research, seepage under irrigation canals and water supply reservoirs has been identified as potential sources of water loss. A geophysical technique called resistivity was applied to six irrigation reservoirs at varying elevations and geology to determine areas of active seepage. Initial results showed a perched water table approximately 3 feet to 20 feet from the surface. To quantify the rate of seepage, a seepage meter was designed, developed, and applied to the six reservoirs that were analyzed using resistivity. Contrary to current understanding, all reservoirs showed a net influx of water, shifting focus on management of the perched water table to minimize seepage losses. This past year three more reservoirs were surveyed. A ponding study was conducted on a large reservoir underlain with sandy soils. The results showed seepage occurred but at one-third of the previously estimated rate. Also, state-of-the-art Doppler flow meter technology was tested on six canal lengths to determine seepage losses under the canals. With accuracy within 5-10%, the methodology is well suited to stream flow measurements, however, the accuracy may not be adequate for estimating losses in canals. The method is currently being refined to determine if it may provide realistic seepage losses in the canals. Quantifying reservoir and canal losses will allow more efficient management of irrigation water and more sustainable biofuel production in Hawaii. Work was initiated to parallelize the SWAT code to run large, spatially detailed basins efficiently on supercomputers at the Hawaii Supercomputer Center. ARS scientists have been collaborating with scientists at the University of Hawaii to recode SWAT to execute multiple subareas on individual processors of a supercomputer. Once the model has been recoded, model runtime will reduce from hours or days to minutes. This work will also benefit the CEAP (Conservation Effects Assessment Project) by reducing run time for national conservation assessment simulations to minutes, thus allowing rapid response to policy makers.