Assessing Long-Term Groundwater Quality Trends Using Historical Water Quality Monitoring Data

Abstract

Groundwater is an important source of public drinking water. Its quality may change gradually as water continues to pass through reservoirs for many years. The study assessed long-term groundwater quality trends. Historical observational data from USGS's GAMA Prioritization Basin Project, California were used. The Google Collab experiment that was implemented used public data releases by the U.S. Geological Survey from 2004 to 2023. The dataset included 444 study sites and 145 components. It also included 21,461 double comparison records for the tenth. The analysis cleaned up the tables and converted the reported values to numbers. Handle the blocked values on the left with a simple half-term rule. Then compare the previous and subsequent results of the same wells. That's why Wilcoxon's double-sign rating tests were used. The Spearman relationship was used to examine the relationships between different species. The calculated results showed strong reductions in several ingredients. It included methyl tart-butyl ether, 1,2-dichlorobrane, 1,2,3-trichloropropene, fluoride, perchlorate, and tritium. The results also showed an increase in the amount of silver, ethrazine, strontium, calcium, magnesium, alkalinate, chloride, sulfate, manganese and uranium. This pattern points to a combination of natural and human control over groundwater quality. The use of agricultural land, urban inputs, old chemicals, and water bodies can influence trends. Studies show that public observational records can help in a clearer assessment of trends when the data is processed carefully.