CABI Blog

In a news item I read in the IWA publication online, Water 21, it was reported that the Los Angeles Department of Public Works has agreed a new law that will require the use of one of several means of capturing, reusing or redirecting rainwater runoff such as rain gardens, infiltration swales and rain storage tanks in new build projects. Other changes proposed in the law include installation of permeable surfaces. Why should we capture and re-use rainwater? Read on to find out.

Clean
fresh water is essential to life and, at the same time, water is one of
the
world’s scarce resources, with around 1.1 million people in the world
today not
having access to safe clean water. Yet most of us still take water for
granted.
The European Environment Agency stated that since the Industrial
Revolution,
unfortunately, most of Europe’s rivers have been treated as a convenient
way of
transporting waste to the sea. This practice has not only affected the
biodiversity of thousands of kilometres of waterways, but is also
causing
pollution to coastal and marine waters and is harming human health.

While
we
have been successful in combating pollution, society and economies has
experienced an ever increasing demand for water of good quality and the
result
is that several regions across Europe are now facing water scarcity, due
to
increasing populations, so not just sub-Saharan Africa suffers
water-related
problems. In 2008, 1.4 billion people lived in regions where existing
water
cannot meet the agricultural, municipal, and environmental needs for
all.

Global
warming and climate change might make water availability even more of a
problem. If the earth’s temperature increases, an increase in temperatures of
surface water bodies and groundwater is also expected. The effect of climate
change on rising water temperatures and its implications for water quality was
studied by researchers at The Swiss Federal Research Institute of Aquatic
Science and Technology (EAWAG), using various models and compiling long-term data series for groundwater
temperatures for the first time. These have shown that groundwater at Rheinau
(Canton Zurich) increased by around 3 ^oC in the winter since the
1950s, while oxygen content has constantly declined.  In the absence of oxygen, iron and manganese
are dissolved below the surface and must be removed before the water can be
supplied to users. In lakes, higher temperatures can promote the spread of cyanobacteria
(blue-green algae), which will degrade water quality further. Microorganisms
generally grow more rapidly in warmer water, resulting in an increase in toxins
or taste and odour compounds. This means, in the future, more elaborate
treatment methods might be required in places where drinking water has
previously been supplied untreated or after only simple processing. 

In LA,
the proposed rainwater harvesting law would require new homes, larger
developments and some redevelopments to capture and reuse runoff generated in
rainstorms, which would normally end up in the sea. An article in the LA
Times added “the ordinance approved in January by the Department of Public
Works would require such projects to capture, reuse or infiltrate 100% of
runoff generated in a ¾-inch rainstorm or to pay a storm water pollution
mitigation fee that would help fund off-site, low-impact public developments.”

I think
this law is a positive step towards conserving our most precious resource and
should be made law in all major cities, at least. And why not go all the way
and require new developments to install rainwater harvesting and purification
system? This would mean all the water supply, including drinking water, to all houses and businesses in a new
development would be supplied by rainwater, when available, and switched to mains
water only in drought periods.

Link to L
A Department of Public Works

Link to L
A Times article

Visit CAB
Abstracts database to consult 251 records on water safety
issues, 366 on water
security and 167,000 records on water
resources.

Photo credit: uk-energy-saving.com