The awards aim to increase awareness of what can be achieved and inspire future projects and transformational change.
As well as the open spaces and agriculture category, this year an urban greening category has been introduced, focusing on green roofs and green walls.
SWIG marketing director Neal Landsberg said the projects involved were "pioneering a set of solutions that will transform living in cities and suburbs and beyond".
Projects that are likely to be successful include those that "bust" myths about the environmental costs of building and the monetary costs of green building, demonstrate value for money and return on investment, and monetise the value of sustainability.
Nominations are due by September 30. Projects need to be ongoing or to have been completed within the last two years. Go to sustainablewater.org.uk/awards.html to find out more.