This blog will give you a rundown of various strategies and design considerations for water conservation, a critical aspect of designing sustainable sites.
It will mostly apply to landscape designers and architects who use Vectorworks Landmark, but if you use Vectorworks Architect, you’ll find the information helpful for a broader understanding of sustainable solutions.
Let’s first review terms to understand while thinking about water conservation.
Non-potable water – Non-drinkable water used primarily for irrigation.
Wetlands – Areas of soil that can hold water for 20 or more days, filtering it in the process.
Hydric Soils – Soils that can sit wet. They typically comprise a wetland.
Floodplains – Areas at risk of flooding. Accounting for floodplains in site design is crucial for both liability concerns and to reduce the amount of runoff into the water source in case of a flood.
GIS – An acronym for geographical information systems, GIS files contain real-world data represented in the form of points, lines, or shapes that assist in your planning. Certain GIS files note wetlands and floodplains.
Water Budget – A water budget provides a baseline for how much water you can use on a site. Generally, to achieve water balance, inflows to any water system must be equal to outflows plus change in storage during a time interval. Some municipalities provide a water budget, and for others the baseline isn’t provided — regardless, in areas where submitting a water budget isn’t required, it’s recommended to work towards LEED or SITES water budget guidelines anyway.
Working Within the Water Budget
Using more water than is budgeted can cause the appointing party to disapprove your proposal, sending you back to the drawing board. Often, a water budget is given by the local municipality based on use patterns and benchmarks throughout the area.
Here are some ways to reduce potable water use.
1. Collect water from rooftops.
A simple principle, but one that deserves mention. A lot of water flows off rooftops during a rain event, and you can use this water for other site needs. You can collect this rainwater in a cistern or other receptacle.
You just need to check if the rooftops were treated with any chemicals that will harm plants if you irrigate with this runoff. Some roofs contain copper, which you don’t want tarnishing the plants you’re working so hard to hydrate.
It’s simple to account for rooftop water runoff in the early design phase, too. You can quantify how much will be collected based on regional data and roof surface areas, all of which can be appended to smart geometry in Vectorworks Landmark.
2. Do a slope analysis and place a bioretention pond or rain garden at a low point where water will flow towards.
Water will collect in the bioretention pond after flowing down the slopes. This source of water hydrates the immediate area and allows you to run pipes to recirculate that water to areas of the site that need it. The bioretention pond also slows and treats onsite stormwater runoff.
3. Draw hydrozones and group plants with similar water needs.
Designing hydrozones allows you to group plants with similar watering needs together. That way, you can keep the amount of irrigation for each zone constant and ensure that your plants are getting the right amount of water. This ultimately saves water because you reduce the amount of overwatering that occurs.
Hyrdrozones shown in blue.
In Vectorworks Landmark, you can use the intelligent Landscape Area tool to designate areas as hydrozones, the parameters of which can be managed within the Object Info palette (OIP).
Maintaining High-Quality Water
Sustainable site design is as much about reducing use of potable water as it is about maintaining a healthy level of water quality. The more polluted your irrigation system, the worse off site vegetation is.
1. Maximize use of native plants.
Native plants may be less water hungry due to being locally acclimated. They also require less chemical treatment or unnatural additives, which means less chemical runoff and better water quality.
2. Minimize use of fertilizers, pesticides, and fungicides.
Fertilizers help plants grow and are regarded as an easy way to achieve a blooming garden. Fertilizers contain harmful chemicals, though, and using too much pollutes your soil and can even harm plant growth. Instead of relying on fertilizer, consider testing your soil for the nutrients it offers and select plants that flourish with those nutrients.
The same principle applies with pesticides and fungicides. These chemicals pollute the irrigation system. Where possible, seek alternative means to achieve their effects.
3. Retain existing vegetation.
In a site design process, keep as much existing vegetation as possible instead of digging it all up and replacing it with new growth. This green infrastructure is meant to slow down or absorb water.
4. Identify and fix erodible slopes.
Erodible slopes are generally steeper slopes that water travels down quickly, capturing sediment and particles and transporting it into the waterway. Erodible slopes can be fixed by regrading and/or planting vegetation to slow and treat stormwater.
5. Design bioswales to slow and treat stormwater.
A bioswale is a vegetated swale designed to redirect water. Unlike a concrete swale, bioswales are made of plants, penetrable soils, and other elements that encourage water to seep into the earth instead of carrying particles into the waterway. Learn more about bioswales in this blog.
6. Use permeable surfaces.
Permeable surfaces are penetrable and allow stormwater to collect in the soil instead of running into local infrastructure. Permeable surfaces can include pavers, porous concrete or asphalt, or pedestal paving systems.
The depth of gravel underneath a permeable surface can change depending on how much water you want to collect before slowly draining into the soil — Hardscape objects in Vectorworks Landmark can define depths of each material, giving you the ability to make calculations and informed decisions.
Looking for more information on water conservation strategies for sustainable site design? It’s a passion of our landscape industry specialist, Eric Gilbey — check out his webinar to learn from a true master.