1. Andean dams: A regional and national summary of statistics with a focus on Hydro Electric Power (HEP) provision Leonardo Saenz and Mark Mulligan King’s College London Water productivity is defined here more broadly than the measured of crop per drop defined by the Challenge Program for Water and Food (CPWF). In the Andes we have to consider water for food production but also water for the production of hydro-electric power (HEP), for use by large urban populations and for the important industries of the region as well as water for the maintenance of environmental flows. Whilst our Andes-scale analysis will look at the agricultural productivity of water we will also take a broader view of productivity. There are a significant number of dams in the Andean region. They are and will continue to play an important role for both an efficient supply of large energy demands, from both mountain and lowland populations in the Andean countries, and to contribute to the current fight against global warming. With a number of around 174 dams the region firstly, harvests surface runoff provided by about 10.5% of the Andes (around 389190 km2), represented as the total watershed area, which drains into dams; and secondly, enjoys a storage capacity of at least 80300Mm3. Such current infrastructure allows the region to enjoy a significant hydroelectric installed capacity, which being of at least 20000MW, is likely to be the largest source of energy in the region. Nonetheless, this estimate is likely to be highly underestimated. While hydroelectric installed capacities are relatively well reported in Colombia, this information is precarious in the other Andean Countries excepting Argentina, Chile and Venezuela. Similar information gaps are observed in order to account for other dam uses in the region such as irrigation and flood protection capacity. An improved and standardised regional data system on dam census and their productivity is increasingly important to study the role that dams play and will continue to play for current and future energy and water planning and developments in the region. In a country basis the Andean dam census indicates that out of 174 dams, 58 are found in Argentina, 46 in Colombia, 35 in Peru, 15 in Venezuela, 8 in Chile, 6 in Ecuador and 6 in Bolivia (abstracted from the Tropical Database of Dams (TDD) Mulligan and Sáenz 2008). Similarly, in a national basis the distribution of watershed areas draining into Andean dams shows that around 81% is found in Argentina, around 10% in Colombia, 10% in Chile, 6.5% in Venezuela, 5% in Peru, around 4% in Ecuador and less than 1% in Bolivia. Finally, the storage capacity is largest for Argentina with just below 50% of the Andean capacity, 16.5% in Colombia, 15.6% in Venezuela, close to 8% in Ecuador, around 5.6 in Chile, 5.3% in Peru and below 1% (0.3%) in Bolivia. Figure 1. Andean dams. Location and draining area (Source: Sáenz 2009).