To: Michael Brown
From: Katherine Midkiff
Subject: Analysis of Vashon Groundwater Modeling Report
Date: June 7, 2016
Introduction
This analysis is being written in order to evaluate the “Vashon-Maury Island Hydrologic Modeling: Technical Report” and determine whether or not the results of the report are adequate enough to be used for future regional groundwater planning (“ESS 454,” n.d.). I will make this determination by taking note of how well the technical report provides answers to the “needs” that a proper technical report for a groundwater system should address (“ESS 454,” n.d.).
The two main questions and or “needs” that the report was developed to answer are first, will the growing population be supported by the groundwater supply? …show more content…
The elements that detracted from providing quality answers consisted of: 1) For Shingle Mill Creek the model does not do such a good job during the rainy season, in fact during the rainy season the model over-predicts the baseflow as well as under-predicts the peak flow (DHI Water and Environment, 2009; “Case,” n.d.). 2) Also for Shingle Mill Creek the model predicts that in late spring and late fall there would be small runoff events that are not supported by any of the data (DHI Water and Environment, 2009; “Case,” n.d.). Overall, including the summer baseflow, a volume error of 31% was estimated, noted from Table 9 in the technical report (DHI Water and Environment, 2009). 3) For Judd Creek there was not very much success overall, there was an over-prediction in the summer of baseflow, 43%, and in the rainy season the baseflow was instead under-predicted. Overall, the volume error for the Judd Creek system was 41%, noted from Table 9 in the technical report (DHI Water and Environment, 2009). 4) In regards to the wells evaluated for the model only 34 wells were selected and examined, this number is not necessarily going to be representative of the entire Vashon-Maury Island groundwater system (DHI Water and Environment, 2009; “Case,” n.d.). These 34 wells were from 4 aquifers and only two of the 34 observations was from the deepest aquifers, this made it difficult to gain a full understanding of what the interaction between baseflow and the Puget Sound was “Case,”
From: Katherine Midkiff
Subject: Analysis of Vashon Groundwater Modeling Report
Date: June 7, 2016
Introduction
This analysis is being written in order to evaluate the “Vashon-Maury Island Hydrologic Modeling: Technical Report” and determine whether or not the results of the report are adequate enough to be used for future regional groundwater planning (“ESS 454,” n.d.). I will make this determination by taking note of how well the technical report provides answers to the “needs” that a proper technical report for a groundwater system should address (“ESS 454,” n.d.).
The two main questions and or “needs” that the report was developed to answer are first, will the growing population be supported by the groundwater supply? …show more content…
The elements that detracted from providing quality answers consisted of: 1) For Shingle Mill Creek the model does not do such a good job during the rainy season, in fact during the rainy season the model over-predicts the baseflow as well as under-predicts the peak flow (DHI Water and Environment, 2009; “Case,” n.d.). 2) Also for Shingle Mill Creek the model predicts that in late spring and late fall there would be small runoff events that are not supported by any of the data (DHI Water and Environment, 2009; “Case,” n.d.). Overall, including the summer baseflow, a volume error of 31% was estimated, noted from Table 9 in the technical report (DHI Water and Environment, 2009). 3) For Judd Creek there was not very much success overall, there was an over-prediction in the summer of baseflow, 43%, and in the rainy season the baseflow was instead under-predicted. Overall, the volume error for the Judd Creek system was 41%, noted from Table 9 in the technical report (DHI Water and Environment, 2009). 4) In regards to the wells evaluated for the model only 34 wells were selected and examined, this number is not necessarily going to be representative of the entire Vashon-Maury Island groundwater system (DHI Water and Environment, 2009; “Case,” n.d.). These 34 wells were from 4 aquifers and only two of the 34 observations was from the deepest aquifers, this made it difficult to gain a full understanding of what the interaction between baseflow and the Puget Sound was “Case,”