Climate Signals in Groundwater and Surface Water System: Spectral Analysis of Hydrologic Processes

Background/Need:
A number of studies in the US and throughout the world have shown existing relations between variability in water resources and climate variability. However, the effect of climate variability on water resources has been largely neglected. Climate variability affects all hydrologic processes to a certain degree, directly or indirectly through other hydrologic or meteorological processes. This study explores the effect of climate variability on hydrologic processes such as precipitation, streamflow, groundwater level, lake levels, and lake ice-cover duration at the regional (Wisconsin and Great Lakes Region), watershed (Trout Lake Basin) and local scales. Coherence analysis is applied to compute the squared coherency between four teleconnections and several climate and hydrologic time series. The teleconnections considered are the Southern Oscillation Index (SOI), Pacific Decadal Oscillation (PDO), Northern Atlantic Oscillation (NAO) and Northern Pacific index (NP).
Objectives:
The main objectives of this research were:

1. 1. 1. To identify periodic forcing in existing time series of precipitation, stream flow discharge, lake levels, groundwater level, collected in Wisconsin and in the Trout Lake Basin in particular. We explored the existence of a climate-related fingerprint in the mentioned time series, and in related data series on Great Lakes levels and lake ice cover duration.
      2. To investigate the coherency between large scale climate signals, regional climate, local climate, regional hydrologic time series, and local hydrologic time series.
      3. To investigate the phase lag between precipitation and groundwater level, for high frequencies.