A New User-Friendly Tool to Estimate Groundwater Recharge from Daily Weather Data and Well Hydrographs

English Abstract:

The estimation of groundwater recharge from well hydrographs is commonly done in groundwater resource assessment projects. However, this task can be cumbersome and time consuming, especially if there are several wells in the study area with many years of data. To address this issue, the open-source user-friendly application named WHAT (Well Hydrograph Analysis Toolbox) was developed. WHAT estimates groundwater recharge at the local scale using a method combining daily weather data and a well hydrograph. First, the application prepares a complete daily weather time-series representative of the well location. For this purpose, data from the Government of Canada website can be downloaded and automatically formatted. Furthermore, missing data can be filled with data from selected neighboring weather stations using a multiple linear regression model. Groundwater recharge is then estimated as the residual of a daily soil moisture balance (DSMB). In a second step, the daily recharge fluxes are substituted into a mathematical model of the aquifer groundwater balance to produce a synthetic well hydrograph. The third and final step of the method consists in the calibration of the DSMB model parameters, based on the comparison of synthetic and observed well hydrographs. WHAT offers several advantages: 1) gap-free weather datasets can be quickly and conveniently set up; 2) recharge is estimated with a rarely used approach combining well hydrographs and weather data; 3) groundwater levels and aquifer recharge can be calculated for the entire period covered by weather records; and 4) it includes a variety of functionalities useful for the interpretation of water level measurements, such as the plotting of air temperature, precipitation and water-level time series on the same graph. The software is available for download free of charge on GitHub (www.github.com/jnsebgosselin/WHAT).