RELATIONSHIPS BETWEEN DISCHARGE AND LAND USE / LAND COVER IN THE ALTAMAHA WATERSHED

Watershed land use / land cover (LULC) changes alter the timing, duration, and magnitude as well as the water quality of stream discharge. However, changes in (LULC) do not affect streams equally. When changes occur in close proximity to streams discharge is more directly impacted and while changes further from the stream are associated with delayed or indirect impacts. Accordingly, our objectives were to 1) determine if (LULC) changes in the Altamaha watershed are associated with changes in discharge metrics; 2) determine which (LULC) changes are most closely related to alterations in discharge; and 3) determine spatial scales at which (LULC) changes are associated with alterations in discharge metrics. Agricultural, developed, forested and wetland area for each sub-watershed was derived from the 2011 National Landcover Dataset. Discharge data was downloaded from the USGS Water Watch program. Focal discharge metrics were minimum, median, maximum as well as 1st and 3rd quantiles.

Our preliminary analyses indicate positive discharge relationships between minimum recorded discharge and both agricultural land use and forest land cover within a 50 m stream buffer. Expectedly, developed land use cover within 50 m of streams was negatively correlated with both minimum recorded discharge and first quartile discharge. Interestingly wetland land cover was negatively correlated with minimum discharge within this buffer scale. Within the 500 m stream buffer, positive relationships between minimum recorded discharge and both agricultural land use and forest land cover were observe. Both wetland and developed land use were negatively correlated with minimum recorded discharge within the 500 m stream buffer. These preliminary assessments indicate associations between (LULC) and discharge metrics in the immediate vicinity of the stream (50 m) and within a larger extent (500 m) of the stream. Decreases in minimum and 1st quantile flows associated with increased developed LULC could be driven by decreased base flow that results from greater surface run off. Future research will repeat these analyses for other major rivers in Georgia to determine if these observations are consistent across watersheds.