The water supply outlook for south central and southeast Colorado as of June 1, 2011 from the NWS in Pueblo, states that snowpack remained below average in the upper Rio Grande Basin on June 1st. Across the Arkansas Basin, snowpack ranged from well above average in the headwaters portion of the basin to well below average across the southern tributaries.
As of June 1st, the snowpack in the Arkansas Basin was at 133% of average overall, up from 112% of average last month and tracking ahead of the snowpack last year at this time which was 32% of average. Much like the Rio Grande Basin, snowpack percentages increased mainly because of cool temperatures, not so much because of new snow. Across the Arkansas Basin, most of the snowpack was in the headwaters portion of the basin. The southern tributary basins were running well below average or had no snow left at all.
The Rio Grande and Arkansas Basins saw near to below average precipitation in May. Water year precipitation totals on June 1st were still below average in both basins. The Rio Grande Bain reported 92% of average, up a little from 91% of average last month. The Arkansas Basin reported 94% of average precipitation, down a little from 95% of average last month.
Overall reservoir storage is running below average across southern Colorado. Storage in the Rio Grande Basin on June 1st was at 70% of average overall, which is down from 79% of average last month and trailing behind storage levels last year at this time, which were around 90% of average. In the Arkansas Basin, storage was at 72% of average overall, which is down from 86% of average last month, and less than storage levels last year at this time which were around 105% of average.