Time series precipitation data will NOT be available for retrieval following the 120-day display period. Although the instrumentation is generally calibrated once/year, the temporary classification means that documented routine inspections and other quality assurance measures may not be performed that would make the data acceptable for publication by USGS standards. This is not meant to say that these data are not good data, but only that these data are guaranteed to be good quality data. Inquiries may be made for data prior to the last 120 days by selecting the "Questions about sites/data?" link at the bottom of this webpage. Why do we collect precipitation data? The precipitation data are collected for 3 main reasons: First, the National Weather Service (NWS) uses the data to help calibrate their weather radar based precipitation data to report more accurate rainfall. Second, the rainfall totals at USGS rain-gages help the NWS issue flood alerts/warnings to local government agencies of projected flooding in or near downstream communities. Third, the data are used by the USGS to give them forewarning of upcoming high flow events at their streamflow gages. This forewarning allows USGS personnel time to deploy a team to the gaging locations to obtain physical discharge measurements of flow during high-flow conditions. Measurements in high-flow conditions are often rare and hard to acquire due to the fast, flashy nature of streams in most of the drainages of Arizona.

ICE EFFECTS ON STREAMFLOW

The formation of ice on rivers can cause discharge values to appear unusually high. Display of these erroneous discharge data may result in improper assessment of flow conditions and misuse of the data. For this reason, display of discharge values for rivers significantly affected by ice may be disabled from view. Even though the discharge hydrograph is disabled the most recent instantaneous value is listed above the graph and may be affected by ice. That Display of discharge data will resume when ice conditions are no longer present. Discharge values for rivers minimally affected by ice will continue to be displayed. Flows for rivers with these conditions appear to increase during the day and decrease during the night.