The Atlantic basin holds more than 97% of all available water with nearly 2,000 km³ per year. Agriculture also accounts for 80% of water use, while domestic use accounts for 14%. The Lake Titicaca basin receives 10 BCM per year, less than 1% of the total. In this basin, agriculture accounts for 66% of total water use, while domestic use accounts for 30%. Key characteristics of the drainage basins "Source": INEI (2007)  External resources of water enter Peru though tributaries of the Amazon, in the Atlantic river basin, supplying 125 BCM annually. The main rivers are Napo, Tigre, Pastaza, Santiago, Morona, Cenepa, and Chinchipe. ANA estimates the total amount of groundwater available on the coast to be between 35 and 40 km³. There is specific data available only for eight valleys on the coast with 9.0 km³ of groundwater available. Around 1.8 km³ of water are actually extracted on the coast. No sufficient information is available regarding groundwater availability and withdrawal in the highland and Amazon regions. Groundwater withdrawal per sector in Peruvian coast (5) "Source": ANA  In 1980, the former National Institute of Natural Resources (INRENA) established an inventory of Peru's water storage capacity, including lakes and dams. Peru has 12,201 lakes, 3,896 of which are located in the Pacific basin, 7,441 in the Atlantic basin, 841 in the Titicaca basin, and 23 in the closed basin of Warmiqucha. INRENA inventoried 186 lakes in operation with a total capacity of 3,028.07 million cubic metres and 342 studied lakes with a total capacity 3,953.04 million cubic metres. According to the inventory, the largest number of lakes in operation were located in the Pacific basin, with 105 lakes and a total capacity of 1,378.58 million cubic metres, followed by the Atlantic basin with 76 lakes and a capacity of 1604.73 million cubic metres. The Pacific basin also has the largest number of studied lagoons, with a total of 204 lakes and a total capacity of 616.62 million cubic metres, followed by the Atlantic basin with 133 lakes and a capacity of 3,006.42 cubic metres. Peru also has 23 dams with a total capacity of 1,941.88 million cubic metres, and 238 studied dams with a total capacity of 44,028.04 million cubic metres.