Soil moisture is an integral part of the hydrologic cycle. Improved understanding of the spatial and temporal variability of soil moisture will result in a clearer picture of how the atmosphere is impacted by varying soil moisture conditions. Since 1996, the Oklahoma Mesonet has instrumented nearly 100 sites with soil moisture sensors at four depths (5, 25, 60 and 75 cm). These sites provide observations every 30 minutes across varying soil, vegetation and climate conditions.

Using the data collected by the Oklahoma Mesonet, monthly, seasonal and yearly averages of soil moisture were calculated from 1997 through 2001. Furthermore, correlations between soil moisture conditions and other meteorological variables were determined. In addition, the impact of two significant droughts in 1998 and 2000 on soil moisture conditions was quantified. The results show that during peak drought conditions, the available soil moisture at crop root depth (60 cm) decreased by ~35% in 1998 and ~50% in 2000 from normal. Even with the onset of winter precipitation, the soil moisture at deeper depths (e.g., 60 and 75 cm) at sites most severely affected by the drought never fully recovered until months of substantial precipitation.