Note: Descriptions are shown in the official language in which they were submitted.
CA 02264440 1999-03-02
-1 -
RAINFALL COLLECTION SYSTEM
Field of Invention
This invention relates to water collection and storage systems. In particular,
this
invention relates to a rainfall collection system for collecting and storing
rainwater as a source of
potable water.
Background of the Invention
Many arid regions of the world suffer from a scarcity of potable water.
Different
methods axe conventionally used to produce potable water, the most popular
being desalination
of sea water. However, desalination is a slow and expensive process and the
cost of purchasing,
installing and maintaining a desalination plant renders it impractical in most
densely populated
regions, particularly inland regions.
Rainwater has heretofore been largely unavailable as a source of potable water
in
many regions where it rains only intermittently, because it is difficult to
collect and store.
During heavy rainfall periods most of the rainwater is lost to the ground, and
reservoirs tend to
lose rainwater in a short time due to evaporation and percolation.
It would accordingly be advantageous to provide a rainwater collection system
which collects large amounts of rainfall and is capable of storing collected
rainwater for extended
periods as potable water.
The present invention provides a rainfall collection system which extends over
a
wide area to maximize the collection of rainfall, and funnels collected
rainwater into a central
storage tube for prolonged storage without evaporation or percolation into the
ground.
CA 02264440 1999-03-02
-2 -
The system of the invention automatically transfers collected water into the
storage tube, and requires minimal maintenance. The cost of collecting and
storing rainwater in
the system of the invention is substantially lower than the cost of
desalination, both in terms of
the cost of purchasing and installing the required facilities and in terms of
maintaining ongoing
potable water production.
The invention accomplishes this by providing a platform consisting of a
plurality
of water-impermeable membrane panels laid over a bed graded with a shallow "V"-
shaped
profile and having a swale running along the apex of the bed. A flexible
watertight collection
tube disposed within the swale beneath the membrane panels collects captured
rainwater through
pumps activated by water accumulating in the bed. Rainwater is thus
automatically pumped into
the collection tube as it accumulates on the membrane panels, preventing
losses due to
evaporation and percolation into the ground. The collected rainwater is stored
in the storage tube
and dispensed to an aqueduct system or tank trucks for transportation to the
desired destination.
In the preferred embodiment the membrane panels axe transparent or
translucent,
allowing maintenance personnel to detect leaks in the panels by darkened areas
of the ground
visible through aerial inspection. The membrane panels may be marked with
coordinate
identifiers, allowing maintenance personnel to readily locate damaged areas
from the ground. A
grid of maintenance corridors interspersed throughout the collection platform
allows access to
the membrane panels for maintenance and repair.
In the preferred embodiment the storage tube is provided with a sediment
filtration system comprising catchment pits located near each end of the tube.
The swale is
pitched slightly downhill from the centre to the ends of the collection tube,
facilitating sediment
collection in the catchment pits.
The present invention thus provides rainwater collection system, comprising a
platform comprising a plurality of water-impervious panels, having a top
surface for collecting
CA 02264440 1999-03-02
-3 -
rainwater and adapted to be laid over a bed having banks graded downward
toward an
intermediate region of the bed such that an apex of the bed is disposed along
an intermediate
portion of the platform, and an inflatable water collection tube disposed in a
swale beneath the
platform substantially along the apex thereof, the water collection tube being
in fluid
communication with the top surface of the platform through a plurality of
pumps, wherein when
rainwater falls on the platform the rainwater accumulates over the water
collection tube and the
pumps are actuated to pump the rainwater into the water collection tube.
Brief Description of the Drawings
In drawings which illustrate by way of example only a preferred embodiment of
the invention,
Figure 1 is a top plan view of the rainwater collection system of the
invention,
Figure 2 is a cross-sectional elevation of the rainwater collection system of
Figure
1 showing the water collection tube in a deflated (empty) condition,
Figure 3 is a cross-sectional elevation of the rainwater collection system of
Figure
1 showing the water collection tube in an inflated (storage) condition,
Figure 4 is a partial transverse cross-section of the platform showing the
preferred
manner of anchoring the membrane panels,
Figure 5 is a bottom plan view of a pump in the rainwater collection system of
Figure 1, and
Figure 6 is a cross-section of the pump of Figure 5.
CA 02264440 1999-03-02
-4 -
Detailed Description of the Invention
As illustrated in Figures 1 to 3, in a preferred embodiment the rainwater
collection
system of the invention comprises a platform 20 and a collection tube 40. The
platform 20
comprises a plurality of water-impervious membrane panels 22 laid in abutting
relation so as to
render the platform 20 substantially watertight.
The platform 20 is laid over a shallow "V"-shaped bed 2 with banks 3 formed in
the ground in any suitable area, preferably in a clay or other relatively
dense base. The banks 3
of the bed 2 may be graded at a pitch of less than 1 °, or may be bowl-
shaped or otherwise graded
toward the longitudinal centre of the bed 2, but should be substantially
smooth to avoid pooling
of rainwater on the platform 20 remote from the collection tube 40. Preferably
the panels 22 are
composed of a lightweight, flexible plastic membrane material which may be
clear, semi-
transparent or translucent to allow for visual aerial inspection. The plastic
is also preferably
treated so as to be resistant to decomposition by ultraviolet light.
As shown in Figure 4 the panels 22 are laid in overlapping relation, with an
anchoring portion 24 of each panel 22 buried to preferably a minimum of 3 feet
to anchor the
panel along its length. The edge 26 of the next abutting panel is heat sealed,
welded or bonded to
the upper corner of the anchoring flap 24 to render the platform 20
watertight.
In the embodiment shown each panel 22 is 103 feet wide ( 100 feet of exposed
panel plus a 3 foot anchoring flap 24), and over 4,000 feet long. The
particular sizes of the
panels 22 and the number of panels used to produce the platform are a matter
of selection
according to environmental and topographical conditions and the amount of
rainfall sought to be
collected by the system.
The platform 20 is provided with a series of maintenance corridors 30
intermittently interspersed amongst the panels 22, which may be surfaced with
gravel to
CA 02264440 1999-03-02
accommodate maintenance trucks. A separate drainage system (not shown) is
provided in the
swale 4, described below, to remove runoff from the maintenance corridors 30.
At the apex of the bed 2 is provided a swale 4, which is essentially a ditch
running
longitudinally along the bed 2. The width and depth of the swale 4 is selected
to accommodate
the collection tube 40 in the fully inflated condition, which in turn is
dependent upon the amount
of rainfall sought to be collected by the system.
The collection tube 40 comprises an elongated watertight bladder preferably
formed from a rugged, flexible and water-impervious plastic or rubber membrane
formed into a
sleeve and having ends 42 welded, bonded or otherwise suitably affixed
thereto. The water
collection tube 40 extends beneath the platform 20 along substantially its
entire length, to collect
rainwater captured by the platform 20 in the manner described below.
The platform 20 is anchored to the water collection tube 40 by a series of
pumps
50, illustrated in Figures 5 and 6, distributed in substantially evenly spaced
relation along the top
surface of the water collection tube 40. The pumps 50, each having a
waterproof casing 56, may
be spaced apart longitudinally every 50 feet or so as in the embodiment shown,
and are disposed
circumferentially offset from the apex of the water collection tube 40 toward
the side walls of the
swale 4, for reasons described below. The top surface of the platform 20 is in
communication
with the interior of the water collection tube 40 through the pumps 50, as
shown in Figure 5.
In operation, the water collection tube 40 is in the empty condition shown in
Figure 2 after installation of the system. As rain falls over the platform 20
the rainwater runs
down the panels 22 toward the swale and begins to accumulate above the water
collection tube
40. The pumps 50, each with water level detectors (not shown), are actuated
when accumulated
rainwater rises to the level of the water detectors. Collected rainwater is
pumped into pump
inlets 52 and through pump outlets 54 into the water collection tube 40, which
begins to inflate.
CA 02264440 1999-03-02
-6 -
As the water collection tube 40 inflates it raises the central portions of the
panels
22, creating troughs 36 along the side edges of the swale 4. The pump inlets
52 are preferably
oriented toward the troughs 36, so the pumps 50 are activated by increasingly
smaller volumes of
water as the collection tube 40 inflates and assumes more of a convex profile.
Thus, even as the
rate of rainwater collection decreases as the rainfall diminishes, the pumps
50 are able to
continue pumping the rainwater into the collection tube 40. If desired the
troughs 36, which are
not directly supported by the ground, could be formed from a thicker membrane
or reinforced
with additional membrane layers.
Water is dispensed from the collection tube 40 through pipes 60 at one or both
ends 42, into an aqueduct or other piping system (not shown) or into tank
trucks, for
transportation to the intended destination. The swale 40 is preferably graded
slightly downhill,
from one end 42 to the other end 42 if only one dispensing pipe 60 is used as
in the embodiment
shown in Figure 1, or if pipes 60 are disposed at both ends 42 the swale 40 is
graded downhill
from approximately the longitudinal centre of the tube 40, so that water will
not pool in the
collection tube 40 and sediment collected with the rainwater will flow toward
the dispensing
pipes) 60.
Sediment catchment pits (not shown) having coarse and fine filters for
separating
stones, plants, sand, sediment and the like from the collected water before
dispensing, may be
disposed upstream of or in communication with the dispensing pipes) 60. A bean
(not shown)
may be erected around the platform 20, or adjacent to those portions of the
platform 20 which are
subjected to winds, to reduce the accumulation of sand and debris on the
platform 20.
The maintenance corridors 30 may be used to gain access to all portions of the
platform 20 for periodic cleaning and maintenance. Visual inspection by aerial
examination
would also be conducted periodically, and any leaks in the panels 22 would be
readily visible as
darkened portions of the ground beneath the clear or translucent membrane
panels 22.
CA 02264440 1999-03-02
Maintenance personnel would be directed to the affected area by reference to
coordinate
markings 28 on the panels, shown in Figure 1, corresponding to a map matrix
representation of
the platform 20.
It will be appreciated that although the platform 20 in the illustrated
embodiment
is laterally symmetrical, depending upon environmental and topographical
conditions it may be
appropriate in any particular case to have one side of the platform 20 smaller
than the other. In
such a case the water collection tube 40 would not be centred beneath the
platform 20, but the
apex (lower limit) of the bed 2 would still run along an intermediate portion
of the platform 20
and the water collection tube 40 would still be disposed beneath the apex of
the platform 20 in
order to collect rainwater as it accumulates.
A warming system (not shown), which may be electrically or solar powered, may
be optionally disposed on the bed 2 to melt snow in colder climactic
conditions.
A preferred embodiment of the invention having been thus described by way of
example only, it will be apparent to those skilled in the art that certain
modifications and
adaptations may be made without departing from the scope of the invention, as
set out in the
appended claims.
