The USGS developed the SWB2 Model (Westenbroek et al., 2018) to allow users to easily calculate water budget components, and specifically groundwater recharge. For this study SWB2 was used to develop a groundwater recharge coverage, which could then be used as an input to the FloPy groundwater model.
To download output data sets (in .asc format) from the water budget model: Follow This Link
To see maps of island wide water budget components at an annual average resolution: Follow This Link
To download output data sets (in .asc format) from the water budget model: Follow This Link
To see maps of island wide water budget components at an annual average resolution: Follow This Link
Future Climate Scenarios
The water budget calculations discussed so far use input data collected in the late 20th and early 21st centuries, and therefore represent estimates of hydrologic conditions during this period. However, the climate of the late 21st century, and likely beyond, will undeniably be significantly different than it has been in the short period of time since the start of the industrial revolution.
To estimate the potential effects of future climate change on water budget components, and thus future water resources availability in American Samoa, the Tutuila SWB2 model was run with modified input files derived from dynamically-downscaled climate projections for American Samoa. These projections were developed by Wang and Zhang (2016) using a physically-based global climate model. These authors produced gridded-hourly data for precipitation and temperature at 800 m by 800 m grid resolution and simulated three specific scenarios: 1) present-day climate for the years 1990 to 2009, 2) future climate during the years 2080-2099 reflecting a lower-carbon emissions scenario (RCP4.5), and 3) 2080-2099 climate reflecting on a higher emissions scenario (RCP8.5). Water budget results using downscaled rainfall and temperature predictions (Wang and Zhang, 2016). Present-day predictions are shown as depth of water (left column) whereas future predictions are shown as % change from the present-day scenario for the RCP4.5 (center column) and RCP8.5 (right column) scenarios.
The water budget calculations discussed so far use input data collected in the late 20th and early 21st centuries, and therefore represent estimates of hydrologic conditions during this period. However, the climate of the late 21st century, and likely beyond, will undeniably be significantly different than it has been in the short period of time since the start of the industrial revolution.
To estimate the potential effects of future climate change on water budget components, and thus future water resources availability in American Samoa, the Tutuila SWB2 model was run with modified input files derived from dynamically-downscaled climate projections for American Samoa. These projections were developed by Wang and Zhang (2016) using a physically-based global climate model. These authors produced gridded-hourly data for precipitation and temperature at 800 m by 800 m grid resolution and simulated three specific scenarios: 1) present-day climate for the years 1990 to 2009, 2) future climate during the years 2080-2099 reflecting a lower-carbon emissions scenario (RCP4.5), and 3) 2080-2099 climate reflecting on a higher emissions scenario (RCP8.5). Water budget results using downscaled rainfall and temperature predictions (Wang and Zhang, 2016). Present-day predictions are shown as depth of water (left column) whereas future predictions are shown as % change from the present-day scenario for the RCP4.5 (center column) and RCP8.5 (right column) scenarios.