WRTDS

The WRTDS calculation here is based on Hirsch et al. 2010 @ JAWRA

The advantages of this R script instead of the EGRET are that:

1. This script does not require USGS data format.
2. This script provides uncertainty of prediction, or number of replicated time series.
3. WRTDS model is built based on observed flow and water chemistry at a site, and could be applied to other sites that has similar flow regime and catchment/LULC char.