Draft Lakes and Reservoirs Indicator - version:20250213 (Southeast and Midwest Blueprint)

Upstream watershed condition is very important in determining the nutrient, sediment, and contaminant loads entering a lake. All developed and agricultural land cover categories (disturbance) were added to quantify the amount of disturbed landcover that may negatively affect water quality entering the lake. The nearshore zone is of higher value compared with the open water zone for both ecological and cultural reasons. The nearshore zone potentially supports higher productivity of benthos, macrophytes, and is used by many species for spawning. It is also the portion of the lake that is typically most accessible for public recreation. 1. Preparing the NLCD: * a. Using NLCD 2021 set open water values to null – open water should not count toward nearshore landcover condition. * b. Assign each landcover type into categories of “natural” and “non-natural” * c. Create a 9x9 moving window to assess the majority landcover composition in the neighborhood for each pixel. 2. Assign the amount of disturbance in the contributing watershed: * a. Join the attribute table “Archetypes_rawdata_2023-10-12.csv” (LaPierre et al. 2023) to the LAGOS Lakes dataset. * b. Eliminate any lakes that do not have a valid watershed value (removes 3253 or 0.7 % of lakes) * c. Add the upstream watershed amounts of agricultural and developed landcover “ws_nlcd2016_totalag_pct” and “ws_nlcd2016_totaldev_pct” to get “totdev_totag” * d. Classify lake water quality based on the Midwest Glacial Lakes Partnership thresholds for watershed landcover composition and convert to raster: * 3 = if percent developed + percent ag in the watershed is <= 25 * 2 = if percent developed + percent ag in the watershed is >25 and <=60 * 1 = if percent developed + percent ag in the watershed is > 60 3. Nearshore delineation: * a. Use a “negative buffer” to delineate a 100m buffer inside each lake polygon – the nearshore zone – and convert from vector to raster. This step is used to separate open water from nearshore and assign a higher value to the latter if the adjacent shoreline condition is mostly natural. * b. Combine lake boundaries with nearshore zone delineations using “Union” – this step assigns both the open water and the nearshore with values for watershed disturbance. 4. Using results from Step 3b, convert vector to raster to get: * a. the whole lake class of contributing watershed condition. * b. the extent of the open water and nearshore zone 5. Assign raster values of the nearshore zone by multiplying the nearshore zone value (=1) by the moving windows results from Step 1c. Nearshore areas receive a value of 1 if the majority nearshore landcover is natural, and a zero if the majority nearshore landcover is not natural. 6. Using a conditional statement, combine the results as follows: If the pixel is in nearshore zone, add the nearshore value (=1 or 0) to the whole lake contributing watershed condition score (values 1,2, or 3), otherwise the pixel is in the open water zone and receives only the whole lake contributing watershed condition score. 7. Clean up errant pixels caused by non-overlapping LAGOS and NLCD open water using the condition: If the final score is NULL but there is an open water class value, then assign that value to the pixel, otherwise, keep the existing value.