Agriculture Reference
In-Depth Information
lessened through the implementation of on-site rainwater harvesting tech-
nologies with UV-treatment prior to use or consumption.
(1) Description of Current Situation
Although workshop participants have, amongst others, proposed the use
of rainwater harvesting technologies (RWH) (see Section 4.1 and Table
5), at the moment these are not applied in the case study area. This can
be attributed to the lack of capacity needed to construct and operate such
a system, unwillingness to implement a new technology and/or the poor
state of several houses. Houses in the peri-urban areas are built with a
variety of materials, including cement, ceramic tiles and corrugated iron
sheets, asbestos sheets, cardboard and wood. In general, inhabitants of the
peri-urban areas do not pre-treat their water before consuming unless boil-
ing. The application of tUVo's (a UV-treatment technology developed in
México) and chlorination of water prior to use is currently not common.
(2) Potential Application in Case Study Area
The harvesting, storage and utilization of rainwater at domestic level is an
alternative to avoid the overexploitation of the underground aquifers and
the surface water sources in the peri-urban areas of the México City. This
will be possible in the raining season and part of the dry season (Decem-
ber). The average annual precipitation in Mexico City is 807 mm [29],
with the majority falling in June till October. The collected rainwater will
be stored in storage tanks before use. The capacity of these storage tanks
will depend on the water demand as well as if there are also connections
to the centralized water supply system. As the average weekly household
water demand is 0.8 m
3
(with each household consisting of 4 individuals
and based on households with flush toilets as well as pit latrines) a total
water amount of 3.5 m
3
is needed per month. In general, the roof surfaces
of houses in the peri-urban areas of Xochimilco are estimated to be around
36 m
2
[31]. Assuming a 70% collection efficiency (losses and diversion
of the first flush) 4.3 m
3
of rainwater can be harvested in the month with
the highest monthly precipitation (July; 172 mm) and 0.2 m
3
in the month
with the lowest precipitation (December; 7 mm). The highest monthly RW
supply is almost equal to the monthly water demand, which means that
the storage tank can be kept small as water will be used the same month it
