Current status of drought conditions.

Current status of drought conditions.

The latest drought report from the National Drought Monitor shows an expansion of the formerly crescent-shaped EXCEPTIONAL drought zone in the center of the state (up 2.87% in area assumed to be affected).  This represents a revision from March 18th based on state and federal data and consultation and consensus interpretation.

It is important to remember that the maps are compiled from a wide range of observations and that the depicted drought zones do not represent completely homogeneous conditions.  However, the general message is that drought conditions in Nevada's central northwestern counties (Churchill, Lyon, Lander and now part of Humboldt) persist and the outlook has not improved over the past week. 

At the same time, the Truckee Meadows Water Authority recently issued a statement that water supplies from Lake Tahoe and the reservoir system will be sufficient to meet peak demands through the summer months (until the end of August).  This is based on the best projections from information and analyses.  As an example, the Federal Water Master for the Tahoe-Truckee system issues weekly reports that indicate the probability of specific flow rates at different points, from Tahoe to Pyramid Lake.  These represent potential wet conditions (indicated by the 30% trace on the graph below) and potential dry conditions (indicated by the 70% trace on the graph below).  This graph (projected mean monthly flow rates at the U.S. Geological Survey stream gaging site at Farad (just upstream of the Nevada/California border) estimates that with all flows combined (that means natural flows in the Truckee and releases from the upstream reservoirs) supplies may be sufficient to meet the Floriston rate (more on what that is in the next post) under the wet (30%) and medium wet (50%) scenarios.  However, if our snowpack and reservoir storages remain low and we have a dry (70%) scenario, this may lead to some difficulties meeting the Floriston rate as the summer progresses.  It is important to remember that the projections on this graph represent current observations of the snow pack and reservoir storage--winter snow accumulations may continue, which means the projections will likely change as conditions change.