Rainwater and Irrigation Analysis

Challenges

Integrating run-off water into an ecological design that would meet or exceed the clients’ irrigation needs for existing and future vegetation was a key challenge. Another was balancing the costs and potential benefits between an expensive, labour-intensive rainwater harvesting system that would provide a clear source of irrigation water; and earthworks that would store water in soils and vegetation, be cheaper and no-maintenance, but not provide an easily accessible storage of water.

Key Elements

• Cost-benefit analysis of residential water consumption showed that at current irrigation levels, rainwater harvesting would be cost prohibitive
• Reduced irrigation substantially with only limited die-back of vegetation, and survival and persistence of site-appropriate species
• Substantial financial savings (>5x) from thorough site analysis and installation of small-scale earthworks, rather than rainwater harvesting system
• Reduced-scale rainwater harvesting installed to top up outdoor pond
• Rolling dips in existing driveways to capture overland run-off, directed to two swales for perennial fruit trees, shrubs and herbs

Update

As expected, there was some vegetation die-back in growth; however, despite a dramatic reduction in irrigation, no plants were lost completely and they continue to increase in hardiness over time (e.g. deeper root systems from less frequent and lighter irrigation).  Utility bills are significantly lower, and run-off no longer a problem for either the main or secondary access roads. In the swales, planted vegetation grows abundantly.