Dear Dr. Puranadare,
You have raised very valid points for discussion. As these points required inputs from our CWC experts, it took some time to get it.
The replies to your questions are as below:
1. To what extent Distributed & Ensemble
Models models are being used in India? Any example & its experience?
a)
Distributed models:
Distributed models capture the spatial distribution of input
variables like rainfall, temp and physical parameters like land use, soil,
elevation etc. The recent study on water availability using spatial inputs for
all the basins in Basin planning unit of Central Water Commission are done
based on distributed Modelling ( 56m LULC resolution)
http://www.cwc.gov.in/main/downloads/Reassessment%20of%20Water%20Availability%20-Main%20Report.pdf
IIT Delhi used the distributed SWAT model for climate
change impact analysis for Ganga basin. Besides, the fully distributed models
like SWAT, quasi distributed model like WMS and others are in use in academic
institutes and other research institutes.
b) Ensemble
models:
The multi-model ensembles are expected to bring out more reliability in
the model outputs regarding the future runoff regimes of the basins than that
could be brought about using individual models. IMD has the operational forecasts
models on short to medium range for various user specific applications like
public weather forecasting, agriculture, hydrology, disaster management
etc.
Water
availability is affected by the anticipated changes in temp, precipitation,
atmospheric and oceanic circulations and other climate variables depending on
the scenarios. The climate change impact on ET, rainfall, runoff and water
availability has been shown to be affected by the uncertainty associated to
climate scenarios. An ensemble of hydrological models displaying a range of
complexity is used for research in IITM, IMD and NCMRWF. In 2007, a new statistical forecasting system based
on the ensemble technique was introduced for the seasonal rainfall forecasting
over the country as a whole.
IITM and IMD
use the method to improve the accuracy, reliability and range of weather
forecasts through the use of ensemble and multi-model ensemble techniques.
Besides, National Centre for Medium Range Weather Forecasting, Noida uses global ensemble prediction system of UKMO with 50 ensemble members.
Seasonal and extended Range Prediction group of IITM has been providing
experimental real-time forecast of the active-break spells of Indian Summer
Monsoon Rainfall since 2011 up to 4 pentad lead using an indigenously developed
Ensemble Prediction system based on Climate Forecast System Model. The EPS
generates a large number of forecasts from different initial conditions so that
the expected forecast and also the expected spreads or uncertainties in terms
of probability from this forecast can be informed.
2. What is the
mechanism to document changes in basin properties & notify the
same? Its periodicity?
Land use changes may have significant impact
on erosion and agricultural soil properties, including soil
degradation by acidification, leaching and organic matter depletion. Land
use pattern is a key factor for landscape planning and development. There is no
clear cut mechanism to document changes in basin
properties and notify the same. In case there is a distinct change in the land
use pattern due to anthropogenic or natural phenomena, the same can be
documented in the LULC change. Also,
there are no guidelines for periodicity
as such. But annual changes are mapped by NRSC, Hyderabad through lULC mapping.
NBSS Nagpur maps the soil texture changes through survey periodically.
3. How authenticity & reliability of hydrological data is
ensured in practice?
Water resources cannot be managed, unless we know where exactly they are,
in what quantity and quality, and how variable they are likely to be in the
foreseeable future. The hydrological data must be of authentic and reliable. The
data quality required for a specific purpose will depend to a significant
degree on the requirements of the application areas and it needs to be
recognized that not all data is fit-for purpose in all application areas.
BIS/ISO standards are available in
this domain for establishing the gauges, recording the water levels, measuring
discharges in the open channels etc. By strictly following the prescribed
methods and necessary precautions the reliability and authenticity of the data
can be ensured. The hydrological data collection network has to be automated (through
advanced types of sensors and telemetry) to avoid systemic & human errors. O
& M of this network also has a large impact on the quality &
reliability of the data. In CWC, regular inspection of sites are carried out by higher officials (viz. Sub
Divisional, EE,SE and CE) and river
discharge also observed with additional check current meters to ensure the quality of the data.
In addition to the above, number of statistical tests like Screening,
Homogeneity Test, Randomness Test, Consistency Check, Primary and Secondary
Validation etc. are applied to validate the correctness of hydrological data
and relevant acceptance, rejection or modification are generally applied to the
dataset before being used in any hydrologic analysis. Software packages like
HYMOS, SPSS or SYSTAT are very useful.
4. Should it not be mandatory to have qualified hydrologists in
Water Resources Department to give justice to all matters related to hydrology?
Yes, it is always better to have qualified
hydrologists and water resources professionals to deal with planning, design of
water resources and WR modeling in particular using domain knowledge providing
hydrological inputs.
The very objective of the present course is to
create a pool of trained hydrologists across various Organisations; who would
have necessary knowledge & skills to
give justice to all matters related to hydrology.
Thanks for starting the discussion on the subject.
All the best.
Dattakumar Chaskar