DOI: 10.5061/dryad.3r2280gsm
title: Data from: Projected land use changes will cause water quality degradation at drinking water intakes across a regional watershed

description: Forest conversion to development threatens the ability of watersheds to
 provide stable and clean water supplies. Water managers are targeting
 forest conservation as a source water protection strategy to maintain
 healthy watershed function in developing areas, especially upstream of
 drinking water treatment facilities. Understanding the role of current
 forest cover in safeguarding these facilities is therefore crucial. We
 used the Soil and Water Assessment Tool (SWAT) to examine the relationship
 between upstream forest cover and downstream water resources under both
 current (2020) conditions and multiple projected land use scenarios for
 2070 in the Middle Chattahoochee watershed, USA. We investigated the
 extent to which existing forest cover benefits water quality at 15
 drinking water intake facilities within the watershed. Our analysis of
 four land use change scenarios revealed that forest conversion and
 increased development resulted in higher average annual concentrations of
 total suspended sediment (TSS) and total nitrogen (TN) at 13 out of 15
 intake facilities, with potential increases of up to 318% for sediment and
 220% for nitrogen. Conversely, concentrations decreased relative to the
 baseline when upstream agricultural land was converted to forest cover or
 new, low-intensity development, suggesting that certain types of
 development may improve water quality compared to maintaining agricultural
 land. Our results also indicated that extreme nitrogen and sediment
 concentration events – defined as days exceeding the highest 10th
 percentile of baseline concentrations – could become 3.6 to 6.6 times more
 frequent in the future, respectively. Notably, forest conversion to new
 development upstream of intakes with smaller subwatersheds could reduce
 water quality for utilities serving smaller towns and rural areas, which
 may have limited resources for managing this challenge. Our findings
 highlight vulnerable intake locations and underscore the benefit of forest
 conservation for source water protection under future land use change.
description: # Data from: Projected land use changes will cause water quality
 degradation at drinking water intakes across a regional watershed
 [https://doi.org/10.5061/dryad.3r2280gsm](https://doi.org/10.5061/dryad.3r2280gsm) ## Description of the data and file structure This dataset contains the data required to replicate figures and tables from Gay et al. (2025), which assessed the effect of land use change on water quality at drinking water intakes in the Middle Chattahoochee watershed. Data is comprised of spatial and tabular data. Spatial data includes the boundary from SWAT watershed delineation, a shapefile of the Chattahoochee River, and land cover from the various scenarios. Tabular data is comprised of outputs from the SWAT model scenarios. All scenarios, sources, and methodologies are detailed in Gay et al. (2025).   ### Files and variables #### File: dryad\_data.zip **Description:** To access data, download the dryad_data.zip folder. Data is structed in two main folders: spatial_data and swat_outputs. File structure is as follows: Spatial Data: * flow_lines: this shapefile line data represents the Chattahoochee River derived from the National Hydrography Dataset (NHD).  * watershed_boundary: this shapefile polygon data represents the boundary for the Middle Chattahoochee produced through the SWAT watershed delineation step. * land_cover:  * all_forested: a raster where all terrestrial land in the 2011 National Land Cover Dataset (NLCD) raster for the Middle Chattahoochee was transformed to mixed forest cover (NLCD class 43; SWAT class FRST). * all_developed: a raster where all terrestrial land in the 2011 NLCD raster for the Middle Chattahoochee was transformed to medium-intensity development (NLCD class 23; SWAT class URHD). * 2020_basemap_NLCD: a raster representing the basemap for the baseline scenario. * 2070_hadSSP3_NLCD: a raster representing land use for the LG-1 scenario (low growth; HadGEM2-ES and SSP3) * 2070_hadSSP5_NLCD: a raster representing land use for the HG-1 scenario (high growth; HadGEM2-ES and SSP5). * 2070_mriSSP3_NLCD: a raster representing land use for the LG-2 scenario (low growth; MRI-CGCM3 and SSP3). * 2070_mriSSP5_NLCD: a raster representing land use for the HG-2 scenario (high growth; MRI-CGCM3 and SSP5). SWAT Outputs: * all_developed: SWAT model outputs from the all_developed scenario, including outputs for .rch, .cio, .std, .hru., .std., .sub. * all_forested: SWAT model outputs from the all_forested scenario, including outputs for .rch, .cio, .std, .hru., .std., .sub. * baseline2011: SWAT model outputs from the scenario used to calibrate the model (2011 NLCD), including outputs for .rch, .cio, .std, .hru., .std., .sub. * basemap2020: SWAT model outputs from baseline scenario, including outputs for .rch, .cio, .std, .hru., .std., .sub. * HADSSP3: SWAT model outputs from the LG-1 scenario, including outputs for .rch, .cio, .std, .hru., .std., .sub. * HADSSP5: SWAT model outputs from the HG-1 scenario, including outputs for .rch, .cio, .std, .hru., .std., .sub. * MRISSP3: SWAT model outputs from the LG-2 scenario, including outputs for .rch, .cio, .std, .hru., .std., .sub. * MRISSP5: SWAT model outputs from the HG-2 scenario, including outputs for .rch, .cio, .std, .hru., .std., .sub.