A survey of the sedimentation of Lago Loiza (Carraizo), in north-central Puerto Rico was conducted during July 1985. The survey showed that the actual capacity of the reservoir has declined from 21,700 acre-ft in 1953 to about 10,100 acre-ft in 1985. Sedimentation is depleting the reservoir 's capacity at an average rate of about 439 acre-ft/yr, or about 1.8%/yr of the original capacity. The increase in capacity of 2,400 acre-ft produced in 1977 when flashboards were installed, has now been nullified by sedimentation. Under optimal conditions the remaining usable life of the reservoir is estimated to be about 23 years. (Author 's abstract)