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SPDSS Memorandum <br />To: Ray Alvarado, Ray Bennett <br />From: Riverside Technology, inc., Amnon Nevo, Tim Martin, And Nils Babel <br />Subject: SPDSS, Spatial System Integration Component Task 96 -River Network and Key <br />Structures Location Products <br />Date: 10 March 2005 <br />1. Introduction <br />This memorandum describes deliverables 96.2 and 96.3 prepared under Subtask 96.3. The objective of <br />this subtask includes the following: <br />Create a linked river network layer using the procedure proposed in Deliverable 96.1. <br />Locate and integrate into the network SPDSS key diversion structures. <br />Deliverable 96.2 is the river network and deliverable 96.3 is the location of the key structures along the <br />network reaches. <br />2. Approach <br />As proposed in Deliverable 96.1 -the memorandum `Approach for Linking NHD and HydroBase Spatial <br />Data', the river network was created using the National Hydrography Dataset (NHD). NHD is available <br />for download from the USGS FTP site. NHD is downloadable by subregion (4-digit HUC) and by <br />subbasin (8-digit HUC). Medium resolution data for the whole study area was downloaded in two <br />batches: one for subregion (4-digit HUC) 1019, which covers the South Platte basin, and another for <br />subbasins (8-digit HUC) 10180001, 10180002, and 10180010, which cover the North Platte basin in <br />Colorado. <br />Each download batch is provided as a separate personal geodatabase (PGDB) containing its own separate <br />linked network object. To create a single river network for the whole SPDSS study area the data in each <br />of the two PGDBs were merged into a single PGDB and a single network object was built. <br />Once a single network was created for the entire study area, key diversions were located along the <br />network reach. Using automated linear referencing, a table was created that identifies the location of the <br />closest NHD reach to each of the 800 key diversions. The table can be added to ArcMap as a `Route <br />Event' table. The ReachCode attribute is the reach identifier and the Measure attribute identifies the <br />location specified as percent of reach length from the upstream end. The results of the automated <br />referencing were verified by matching the water source name in the diversions attribute table and the <br />GNIS name in the NHD reach table, by the distance of the diversions from the reach, and by visually <br />inspecting the links. As part of the ISFDSS a high resolution (1:24,000) NHD Geodatabase was built. <br />One Geodatabase covers the eastern slope of Colorado and a second Geodatabase covers the western <br />slope of Colorado. The diversions that were linked to the 100k NHD Geodatabase were then transformed <br />to the 24k eastern slope NHD Geodatabase created under the ISFDSS. Table 1. lists the deliverables and <br />the physical filenames under Task 96. <br />Page 1 of 2Riverside Technafogy, lnc. <br />Wnfcr Resuarecs Err~rncering and CuasrnNng <br />