Rainfall, temperature, wind velocity and pan evaporation data were collected from May 1983 to September 1985, in the rice-growing areas of Vega Baja, Manatl, and Arecibo in northern Puerto Rico. Daily values and statistics including mean, standard deviation, extremes, and totals for each month of record were compiled. Descriptions of equipment installation and operation, data processing, and significance of climatological data for rice cultivation are presented.

Introduction 1 Dam and reservoir characteristics 1 Method of survey 5 Actual capacity and sedimentation 8 Trap efficiency of the reservoir 12 Bottom profiles 12 Needs for further study 15 Conclusions 15 Selected references 16 Appendix 1 -Reservoir sediment data summary form 17 ILLUSTRATIONS 1. Map showing location of Lago Loiza in the Rio Grande de Loiza basin 2 2. Diagram showing sources of public water supply for the San Juan Metropolitan area 3. Diagram showing land use in the Rio Grande de Loiza basin, 1985 4 4. Graph showing area and capacity curves for Lago Loiza 6 5-9. Diagram showing: 5. Lago Loiza and cross sections surveyed in 1985 7 6. Streamflow and suspended-sediment discharge during the flood of May 1985 at Rio Grande de Loiza at Caguas 10 7. Streamflow and suspended-sediment discharge during the flood of May 1985 at Rio Gurabo at Gurabo 11 8. Changes in storage capacity of Lago Loiza caused by sedimentation 13 9. Bottom profiles of Lago Loiza 14 TABLES 1. Principal tributaries to Lago Loiza 5 2. Principal characteristics of Lago Loiza and structures 5 3. Comparison of prior and current sedimentation surveys of Lago Loiza, Puerto Rico 4. Comparison of sedimentation surveys conducted by the