San Juan Basin

Observed 1998 April-July volume flows for rivers in the San Juan Basin were below average compared to much above average last year. Based on a sample population of 10 stream gages, spring runoff flows (April -July) ranged from 75%-95% of normal with a median of 85%. Streamflow was above average during March due to much above average precipitation. No gauged river sites recorded flows above bankfull, subsequently, no flooding occurred in the San Juan Basin during the runoff period.

Most of the precipitation fell in March with 140% of average realized, whereas, December through February received much below average precipitation (60%), below average (80%) and average (100%), respectively. Precipitation dropped in April (90%) and May (45%) returning to much below average. However, the water year precipitation for December through May remained near average. The average basinwide snowpack was consistently much below average to below average from January 1^st through April 1^st, reporting 65%, 70%, 70% and 80%, respectively. On May 1st , the snowpack had rebound to near average (110%).

By June 1^st, the snowpack had decreased once again to much below average (55%).