Climate

Ozark Aquifer Climate: Climate is often presented as regional weather averages over a reference period relevant to the environmental system under study. Hawker (1992) observes that while averages would indicate a mild Missouri climate, the climate variation found within the state excludes many expected species due to extremes within those averages. This allows species from many different biomes to live here. In other words the species composition of the state is more complicated than a simple melting pot of surrounding biomes. Most discussions of how climate in the Missouri Ozarks effect groundwater end at precipitation and temperature since they are the normal water cycle entry points. Hawker presents a summary of the climate of the state summarized in Table 1. Greater precipitation adds more water entry into the system. But temperature may encourage evapotranspiration, more interception, and less overland flow, thus subtracting from water entry depending on the response of the vegetative communities to temperature.

The USGS is not water balancing on a static climate model. They are trying to analyze the water balance now and into the future for resource availability projections. In 2018 they ( Clark et al.) state that the average precipitation from 1900-2014 was 43.9 in./year with wetter springs and drier winters and an evapotranspiration rate of 30-35 in./year peaking in summer. The major factors in ground water recharge are climate, soil, topography and land use (Westerman et al., 2016). In a moment of surprise (and citing (Milly et al. cited in Westermann et al., 2016) they declare the policy of hydrological stationarity (vary within known and constant range) is dead, based on climate forced hydrological functions (evaporation, evapotranspiration, river discharge, atmospheric moisture vapor fluxes, ….). The USGS discussion then breaks down into a set of complicated assumptions and models for temperature and precipitation. The Ozarks of 2050 are expected to be 3 ^oF - 6 ^oF warmer with 2%-15% more precipitation in winter and spring with 15% spring downpours occurring more frequently. The author thinks these estimates are in the conservative end of the bandwidth.