Tag Archives: rainwater harvesting

Asian water sensitive urban design

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Here are a couple examples of water-sensitive urban design. First, Bangkok is not doing it right. The city is sinking a shocking 3 to 4 inches per year. The article conflates urban flash flooding with river and coastal flooding, but either way getting lower can’t be good.

Meanwhile, China supposedly is doing it right, building “sponge cities” with political and financial support from the central government. I’m a little skeptical of the public relations campaign after my time in Asia. Still, political and financial support for urban water management are in short supply here in the United States, so I can’t exactly take the moral high ground.

 

Los Angeles Stormwater Capture Plan

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Los Angeles has a new stormwater capture plan out. They seem to focus mostly on the idea of using urban stormwater to recharge aquifers at the watershed to neighborhood scale.

The long term (by 2099) potential average annual capture volume was calculated for a conservative and aggressive scenario. Each was broken down by aquifer and between distributed capture and centralized capture. The fraction of the incoming flow to the City through direct precipitation, applied irrigation and run-on (831,400 acre-feet) that is currently captured in the existing baseline scenario is 11% (92,400 acre-feet). The fraction of the incoming flow to the City that could be captured ranges between 24% (197,300 acre-feet) and 33% (285,900), where the low value represents a conservative scenario and the higher value an aggressive scenario. This represents a captured volume of approximately double and triple the existing volume in the conservative and aggressive scenarios, respectively. As in the existing condition, most of the distributed recharge, and most of the increase in recharge, will take place in the San Fernando Valley and the Los Angeles Forebay area under all scenarios, reflecting well suited infiltration characteristics and the prioritization of Class 1 and Class 2 aquifers. It is important to note that the potential capture over the long term (to 2099) does not reflect the stated goals of the SCMP which will provide an implementation strategy for capture potential over the next 20 years.

This doesn’t really explore the idea of capturing and reusing more water at the site scale. If we really tried to close loops better at that scale, using a whole suite of water conservation, stormwater capture, and graywater tools, I feel like it could go a long way. You install waterless plumbing fixtures first (waterless urinals, composting toilets, urine-separating toilets), where practical, then the lowest-flow fixtures next (low flow showerheads and clotheswashers, dual-flush toilets). Then you capture stormwater in cisterns and rain barrels. Next is graywater – capturing and reusing water from clothes washers and showers. None of this is rocket science – it’s just plumbing, but the potential for creative and user-friendly designs just hasn’t been fully explored yet. People may think that the current generation of composting toilets and rain barrels is not worth the trouble even if they lower our water bills a little bit, so we need to design products that people want, like any other industry that competes for peoples’ attention and dollars.