172 The Future of Water in African Cities
• The change of density can be calculated from the UN population data for the urban extent year of record. A density measure of the historical data could provide additional insight and better parameterization of the model for projecting future changes.
Additional Cartographic References In addition, each map made cartographic use of the following data sets:
Dams and reservoirs: Lehner, B., C. Reidy Liermann, C. Revenga, C. Vörösmarty, B. Fekete, P. Crouzet, P. Döll, M. Endejan, K. Frenken, J. Magome C. Nilsson, J. Robertson, R. Rödel, N. Sindorf, and D. Wisser. 2011. “High Resolution Mapping of the World’s Reservoirs and Dams for Sustainable River Flow Management.” Frontiers in Ecology and the Environment 9(9): 494–502. Available online at http://www.gwsp.org/85.html.
Rivers: For South African cities: Rivers of South Africa at 1:500000 Scale. Resource Quality Services and Chief Directorate of National Geo-Spatial Information, Department of Water Affairs, Republic of South Africa. Last updated in 2003. Available online at http://www.dwaf.gov.za/iwqs/ gis_data/river/All.html. For all other cities: USGS HydroSHEDS, described in Lehner, B., K. Verdin, and A. Jarvis. 2008. “New Global Hydrography Derived from Spaceborne Elevation Data.” Eos, Transactions, AGU 89(10): 93–94. Available online at http://www.worldwildlife.org/hydrosheds.
Major towns: Location and population data set created by MaxMind, available from http://www.maxmind.com/; using population data compiled by World Gazetteer, and available online at http://world-gazetteer.com/.
Political boundaries: National boundaries come from Esri’s World Countries data set. Last updated November 2011. Available online at http://www.arcgis.com/ home/item.html?id=3864c63872d84aec91933618e3815dd2.