34.water harvesting A Lecture By Mr. Allah Dad Khan Visiting Professor the University of Agriculture Peshawar Khyber Pakhtunkhwa Province Pakistan

30.  Urban/rural water harvesting structures:
◦ Tankas, Nadis, Talabs, Bavdis, Tanks, Rapats, Kuis,
Virdas
 Rural water harvesting structures:
◦ Kunds, khadins

31.  Built in the main house or in the courtyard.
 Circular holes made in the ground, lined with fine polished lime, in which raiwater was
collected.
 Tankas were often beautifully decorated with tiles, which helped to keep the water cool.
The water was used only for drinking.
 If in any year there was less than normal rainfall and the tankas did not get filled, water
from nearby wells and tanks would be obtained to fill the household tankas.
 The tanka system is also to be found in the pilgrim town of Dwarka where it has been in
existence for centuries. It continues to be used in residential areas, temples,
dharamshalas and hotels.

32.  They were secular structures from which everyone could draw
water.
 Most of them are defunct today.
 Step well locations often suggested the way in which they would be
used.
◦ Within or at the edge of a village - utilitarian purposes and as a cool place
for social gatherings.
◦ Outside the village, on trade routes - resting places.
 When step wells were used exclusively for irrigation, a sluice was
constructed at the rim to receive the lifted water and lead it to a
trough or pond, from where it ran through a drainage system and
was channeled into the fields.

33.  Nadis
◦ Natural surface depression which receives rain water
from different directions
◦ They receive their water supply from erratic, torrential
rainfall.
◦ Can lead to heavy sedimentation and siltation
 Trees can prevent some of this
 Dredging out the sediment before monsoon can also help
◦ Can lose water by evaporation
 Talabs, lakes are similar
 Toba is similar as well – natural depression with a
natural catchment area

34.  Essentially meant for community use and for religious rites.
 Often rectangular in design, jhalaras have steps on three or
four sides. The steps are built on a series of levels .
 The jhalaras collect subterranean seepage of a talab or a lake
located upstream .

35.  Covered underground tank,
developed primarily for tackling
drinking water problems.
 Usually constructed with local
materials or cement, kunds were
more prevalent in regions where
groundwater is saline.
 Before the onset of rains every
year, meticulous care was taken
to clean up the catchment of the
kunds.
 Cattle grazing and entry with
shoes into the catchment area of
the kunds was strictly prohibited.
 The proximity of a kund to the
house or village saved time and
effort in searching for drinking
water.

36.  10-12 m deep pits dug near tanks to collect
the seepage. Kuis can also be used to harvest
rainwater in areas with meagre rainfall.
 The mouth of the pit is usually made very
narrow. This prevents the collected water from
evaporating.
 The pit gets wider as it burrows under the
ground, so that water can seep in into a large
surface area.
 The openings of these entirely kuchcha
(earthen) structures are generally covered
with planks of wood, or put under lock and
key.
 The water is used sparingly, as a last
resource in crisis situations.

37.  Designed to harvest surface runoff
water for agriculture.
 Its main feature is a very long
(100-300 m) earthen embankment
(khadin bund) built across the
lower hill slopes lying below
gravelly uplands.
 Sluices and spillways allow
excess water to drain off.
 The khadin system is based on
the principle of harvesting
rainwater on farmland and
subsequent use of this water-
saturated land for crop production.

38.  Requirements:
◦ Catchment area: shallow, gravelly and rocky uplands with high
runoff potential
◦ Flood plain or gently sloping plain area (khadin area) where soils
are suitable for crop production
 Before rainfall: kharif crop
◦ If good rain, half grown kharif crop (e.g. bajra) used for fodder,
and rabi crop grown instead
 Khadin area – few salts
 But area just outside khadin bund has salt accumulation;
hence khadin farmers better off than non-khadin farmers
 Maintenance:
◦ Grass on catchment, plus restricted cattle grazing
◦ Periodic cleaning of khadin area, including leveling the land plus
possible removal of deposited gravel and sand

39.  Shallow wells dug in low depressions called jheels
(tanks).
 They are systems built by the nomadic Maldharis,
who used to roam these grasslands. Now settled,
they persist in using virdas.
 These structures harvest rainwater. The topography
of the area is undulating, with depressions on the
ground. By studying the flow of water during the
monsoon, the Maldharis identify these depressions
and make their virdas there.
 They separate potable freshwater from unpotable
salt water. After rainwater infiltrates the soil, it gets
stored at a level above the salty groundwater
because of the difference in their density.
 A structure is built to reach down (about 1 m) to this
upper layer of accumulated rainwater.
 Between these two layers of sweet and saline water,
there exists a zone of brackish water.
 As freshwater is removed, the brackish water moves
upwards, and accumulates towards the bottom of
the virda.
 There are also tank structures where the rainwater is
collected and multiple virdas (wells-in-a-tank) are
built

40.  A rapat is a percolation tank
 There is a bund to impound rainwater flowing through a
watershed and a waste weir to dispose of the surplus
flow.
 If the height of the structure is small, the bund may be
built of masonary, otherwise earth is used.
 Rajasthan rapats, being small, are all masonry
structures.
 Rapats and percolation tanks do not directly irrigate
land, but recharges well within a distance of 3-5 km
downstream.
 Silting is a serious problem with small rapats and the
estimated life of a rapat varies from 5 to 20 years.

41.  To solve the water scarcity, the village
collective started rainwater harvesting.
 They started by repairing the old checkdams
or Johads. Johads are the traditional way of
harvesting rainwater.
 A johad is a crescent-shaped bund which is
built across a sloping catchment to capture the
surface water before it runs off.
 Water accumulating in the johad percolates in
the soil to augment the groundwater. The
groundwater then can be used when there is
no rainfall.
 Over the next few years, the water table in the
ground have been increased through the
Johads. The village needs water for drinking,
sanitation, cooking, cattle and irrigation.
 Water is distributed based on the needs by the
collective. The collective has the following
rules:
◦ All villagers must benefit from the efforts of the
collective
◦ All decisions will be arrived after informal
discussions
◦ All decisions will be strongly enforced
◦ Each person in the collective will be responsible to
carry out the task
◦ Collective will use external help only for guidance
and they will do all the work
Before RWH &
reforestation
After RWH &
reforestation
Johad Check dam

42.  Johad collects water during monsoons
 Later used for cultivation
 Johads became the basis for community
participation with general developmental impact –
fewer migrations, higher participation by women,
micro-credit, etc.
 Decisions on johads taken in local gram sabhas

43.  Water quality of traditional water systems often
does not satisfy drinking water quality standards
◦ Faecal contamination of tankas
◦ Floating organic debris, weeds, etc. in tankas
◦ Excessive presence of chemicals such as fluorides
and nitrates
◦ Breeding ground for mosquitoes
 WHO estimates that 80% of all sickness and
disease in the world is due to inadequate water
and sanitation (from both piped and traditional
systems)

44.  Specifically:
◦ Construction of water sources that cannot be contaminated by
infected persons
◦ Filtration of water
◦ Disinfection through chemicals (such as chlorine)
 Broadly
◦ Community involvement, coupled with health education
◦ Protect the catchment area; fencing it off to keep out cattle and
human beings from polluting the area
◦ Improvements in the design and construction of the catchment
area, storage and withdrawal so as to reduce pollution
◦ Awareness regarding traditional water systems and their health
impact

45.  Importance of reforestation
 Keeping cattle away from catchment