tvalentine

surface volume

Blog Post created by tvalentine on Nov 24, 2014

It's been a while, but my latest GIS adventure has been to work with bathymetry to calculate volumes and surface area for several reservoirs in the Central Willamette Basin.   I obtained a 1 meter DEM from the Corps of Engineers for 3 of the reservoirs and that data was great to work with.  I was missing data for 2 reservoirs, so I obtained a scanned and geo-registered historic USGS quad sheet from the historical archive at USGS on-line, and I used the esri map service called USA Topo Maps that contains a geo-registered topographic image that showed contours for the reservoir. The service is copyrighted by the National Geographic Society, i-cubed (copyright 2011).  This map presents land cover imagery for the world and detailed topographic maps for the United States. The map includes the National Park Service (NPS) Natural Earth physical map at 1.24km per pixel for the world at small scales, i-cubed eTOPO 1:250,000-scale maps for the contiguous United States at medium scales, and National Geographic TOPO! 1:100,000 and 1:24,000-scale maps (1:250,000 and 1:63,000 in Alaska) for the United States at large scales.

 

The USA Topo map service image contained contours for the Falls Creek Reservoir. I was able to on-screen digitize the contours and digitize the river channel to combine into a DEM.  I burned the river channel into my DEM and then was able to compute the volumes.

 

The Blue River historical topo map of 1955 showed the contours of the reservoir area prior to building the dam.  I used this image, in combination with the USA Topo map service to create a contour layer.  I also digitized the stream layer, buffered it, and then burned the stream layer into the newly created DEM. 

 

I found a nifty tool on the web that would allow me to loop through the surface volume tool in ArcGIS Toolbox, and specify the height of the reservoir, the elevation I want to stop calculations at, and the interval for the calculations.  For my analysis I wanted to go from full pool to the lowest pool height, and have a volume and area calculation for every meter in between.  The tool works in ArcGIS 10.0 and 10.1 and is available here:

ftp://lnnr.lummi-nsn.gov/GIS_Scripts/MultiVolumes10/

 

Challenges I had on this project were:

1. figuring out that the historical quad sheet was in NAD 27, and once I projected to match my other data, the areas lined up better. 

2. map service and quad sheet were at different scales, so I had to do some interpretation of the contours.  One had 40 foot contours and the other was 80. 

3. I needed to clip the DEM data to the top of the respective dams, so I wasn't calculating volume downstream from the dam.

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