Augmentation of assimilative capacity
This can be achieved by flow augmentation via impounding
the river to use the water stored during the monsoon
period and released during the dry periods. Artificial aeration
must be done for the stream, its tributaries and the
various open drains carrying the wastewater using diffusedaerators placed at the bottom of the stream, mechanical
surface aerators and creating in-stream cascades. DO levels
can also be maintained by designing the location of the
various outfalls in the river as also described by Bhargava
(1983b) and Bhargava et al. (1995).
The results from the WQI study evaluate the critical
parameters at various locations in the stretch and will help
environmental planners to design, formulate and implement
the pollution abatement strategies. Therefore, to
design any further pollution abatement interventions under
YAP, it is important to perform water quality modeling.
The modeling will help the planners to evaluate the proposed
interventions prior to their implementation. The
environmental auditors and planners must insure that the
sewage treatment plants run to their full capacity.
According to a World Bank report, by 2021, the estimated
wastewater generated by NCT would be 3760 MLD
(Economic Survey of Delhi 2008-09). The recycle and
reuse of treated wastewater is also one of the main
opportunities by which water can be used for irrigation,
horticulture and industrial purposes. It can also be supplied
for cooling the towers in power stations. Other beneficiary
options could be groundwater recharge and the treatment
and reuse of sullage water, i.e., water that does not contain
human excreta, for flushing toilets, etc. Moreover, it is
important to tackle the pollution arising due to non-point
sources of pollution such as from the agricultural fields,
direct human and animal bathing in the river, immersion of
idols, etc.
Therefore, it can be summarized that the control of point
sources as well as non-point sources of pollution are vital
to clean the river. The river can be cleaned by adopting the
management options based on the results obtained from
WQI. River quality modeling must be done for the comprehensive
assessment of total maximum daily load
(TMDL) of pesticides and fertilizers and scenario building
studies. Simultaneously, the flow in the river must be
augmented. The diffuse pollution via urban and agricultural
runoff can be minimized by establishing rainwater harvesting
units within the city and sustainable urban drainage
systems (SuDs). This will not only curtail the runoff and
pollutant loadings, but will also recharge the groundwater.
The agriculture runoff which directly enters the river can
be reduced by constructing filter and buffer strips around
agricultural fields adjacent to the riverbank.