There are primarily two aspects to this: preventing the contamination of pesticides from run-off from the course, and preventing the run-off from washing machinery entering groundwater.
The EU Directive 2006/118/EC deals with preventing and combatting groundwater pollution in the European Union (EU), and includes procedures for assessing the chemical status of groundwater and measures to reduce levels of pollutants – http://eur-lex.europa.eu/legal-content/EN/TXT/?qid=1496827219008&uri=CELEX:32006L0118. You can read a summary of it here – http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=cellar:f41f5a96-0ceb-40ed-8cc8-dc08e195ca82.
In the UK this is enshrined in law in The Groundwater (England and Wales) Regulations 2009 – http://www.legislation.gov.uk/uksi/2009/2902/contents/made, and for Northern Ireland – http://www.legislation.gov.uk/nisr/2016/119/contents/made.
There is Guidance from the Environment Agency – https://www.gov.uk/government/publications/protect-groundwater-and-prevent-groundwater-pollution/protect-groundwater-and-prevent-groundwater-pollution#contents and a handy diagram to help you assess when groundwater is vulnerable to pollution – https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/602590/Groundwater-vulnerability.pdf.
We have several books in the Library that deal with this subject, notably:
These are all available for loan.
An online search for a recent enquirer turned up several interesting research reports:
Advice on wash-down requirements are often discussed in the greenkeeping press, for example – Greenkeeper International – http://www.bigga.org.uk/about-us/magazine/back-issues/05-2012/washdown-arerequirements/01156.html and GMé (formerly Golf Management Europe) in August 2015 which you can download here: