1987 Irrigated Lands for the Mountain Home Plateau: Machine Learning Generated

Mountain Home Irrigated Lands 1987 was created for use in water budget studies in Mountain Home. The area of interest was determined by Hydrology Section staff at IDWR, and a study boundary was given to GIS staff and used to clip the model output. The random forest (RF) model is a type of supervised machine learning algorithm requiring GIS staff to provide manually labeled training data. GIS staff also provide the RF model with several input features, typically raster datasets that help distinguish characteristics of irrigated lands. Mountain Home Irrigated Lands 1987 used the following as input features: • Interpolated Landsat 5 [2] surface reflectance imagery (bands: SWIR 2, NIR, Blue, and calculated NDVI) • 10-meter digital elevation model [3] (including slope and aspect) • Height Above Nearest Drainage (HAND) [4] For additional information on the interpolation process for Landsat imagery, please see below. Additional datasets used only for labeling training data include IDWR-provided Active Water Rights Place of Use for 1987. The accuracy of Mountain Home Irrigated Lands 1987 dataset was verified by several methods. First, a validation test is done by withholding a subset of the training data to evaluate how well the model classifies unseen information. Second, GIS staff will run several iterations of the model with variations of training data, with the goal of improving classification for areas consistently misclassified. This process requires GIS staff knowledge, aided by supplementary datasets, to review the area and make decisions. Once a model iteration is determined as ‘final’, a manual mask is created to correct any remaining misclassification in the dataset. Consistent areas of misclassification for Mountain Home Irrigated Lands 1987 include the region south of Mountain Home between CJ Strike Reservoir and the city, pastures and roads within the Morley Nelson Birds of Prey Conservation Area, and wetlands that originate in the Boise Mountain’s foothills and run into the SRP. Misclassification largely occurred in areas with active water rights, but no visible irrigation in the satellite imagery. Final decisions made for these areas were conservative, relying heavily on both an active water right and clear indication of diverted water and artificial application of water to a given field. References: [1] https://developers.google.com/earth-engine/apidocs/ee-classifier-smilerandomforest [2] https://developers.google.com/earth-engine/datasets/catalog/LANDSAT_LC05_C02_T1_L2 [3] https://developers.google.com/earth-engine/datasets/catalog/USGS_3DEP_10m [4] Donchyts, G., Winsemius, H., Schellekens, J., Erickson, T., Gao, H., Savenije, H., & van de Giesen, N. (2016). Global 30m height above the nearest drainage (HAND). Geophysical Research Abstracts, 18, EGU2016-17445-3. EGU General Assembly 2016.