water sampling method in agriculture

1. Water sampling

2. Background
• Healthy soil is fit for purpose, easy to perform well, friable, holds water and
nutrients and has good drainage capacity. It allows for healthy root growth
and good crop establishment. Soil health cannot be determined by just
measuring crop yield, water quality, or any other outcome. Soil chemical,
physical and biological properties, should be taken into account to describe
a function or perform the capacity of the soil. Thus, soil capacity can be
measured from functional relationships obtained by surveying,
observations, sampling, and remote sensing application
• Water sampling is a way of collecting water from different water levels for
testing or analysis. The aim of sampling is to evaluate the water quality
standards as well as describes water contamination level and other
biological properties
• Usually, water samples are taken annually and semi-annually based on
stability of water source

3. • Obtaining a ‘representative’ water sample.
• The process of taking a portion of water for analysis or other
testing.
• e.g. Drinking water to check that it complies with relevant
water quality standards, or river water to check for pollutants,
or bathing water to check that it is safe for bathing.
• The primary goal of water sampling is to observe and measure how
water quality changes over time and should be repeatedly analyzed
over a period of weeks, months, years, and decades to determine
more precisely how water conditions change.

4. • Parameters of water quality
Water quality is determined by assessing three classes of parameters: Physical, Chemical, and Biological.
• Physical parameters :
• Total Suspended Solids(TSS)/ Turbidity
• Total Dissolved Solids(TDS)
• Temperature
• Taste
• Colour
• Odour
Chemical parameters:
• Dissolved Oxygen(DO)
• Chemical Oxygen Demand (COD)
• Biological Oxygen Demand(BOD)
• Hardness
• Salinity
• pH
• Other elements(Iron, manganese, Arsenic, lead, chlorides, sulphates- dissolved/suspended)
Biological parameters:
• Number/Types of Organisms (Faceal Coliforms)

5. Water quality standard for drinking water in
Nepal

6. Water quality guideline for irrigation

7. • Types Of Water Sampling
•Grab Sampling
•A grab sample is a discrete sample which is collected at a specific
location at a certain point in time.
(The collecting of a sample of liquid or gas in a pipeline, tank or system with the intent of transporting the sample)
•Composite Sampling
•A composite sample is a mixture of grab samples taken at different
times or locations and pooled together to provide one sample.

8. •Sampling Methods
•Systematic Sampling
•Random Sampling
•Judgmental Sampling
•Haphazard sampling
•Stratified Sampling
• Systematic sampling method divides water body into grids whereas
samples are collected from points with an equal distance
• In random sampling method, the water body is divided into grids
horizontally and vertically depending upon the depth then samples
are selected randomly.

9. • Regarding haphazard sampling, it is preferable for a homogenous
system which random sampling points are selected.
• In stratified random sampling, water body is divided into different
strata according to former and later use of the area, nature of
contaminants, etc., and then strata are subjected to further sampling
techniques.
• Judgmental Sampling involves the prior knowledge of the water body
and field observation where samples are collected from various points
according to the probability of contaminants distribution

10. • Sampling Techniques
•1.Sampling Surface and sub-surface water
• Shallow water sampler & deep water sampler are used to sample
water from surface & subsurface of water bodies respectively
• Rinse the sampling vessel with water on site 3~4 times. Care must
be taken to avoid contaminating water to be sampled during rinsing.
• Avoid sampling from very close to the bank.
• Submerge the sampling vessel gently to a depth of about 1 m
(surface) and below 1 m (sub surface).Fill it with the water sample.
• Transfer water sample to the laboratory sample container. If a
composite sample is to be submitted for analysis, pour equal
portions of freshly collected samples into a suitable container

11. Different types of Surface/Subsurface water
samplers
Bucket/Scoop Water Sampler Simple Water Sampler

12. •. Water sampling from bore, wells
• Operate the pump/flush out stagnant water from the pipe.
• Operation time will depend on the depth of the bore and
diameter of the pipe-work.
• Do not sample a newly drilled bore/well or a rarely used one
unless the facility has been pumped for more than 48 hours
• Collect the sample from the tap which is located on the
discharge site of the pump

13. Collecting Runoff Sample:
• A runoff sample is collected from a defined area of land at the
lowest part of the slope.
• Erosion flumes are normally used to trap the eroded soil &
channel the runoff water into collection tanks.
• channel that holds run-off water to prevent it from eroding soil. It
may be made of wood, concrete or, as in this case, hard, moulded
plastic
• The upper part of these collection tanks must be below the flumes

14. Water samples’ preparation
There are some precautions to be followed when preparing a water sample starting
from shifting samples to the laboratory. Careless handling of a sample can produce
highly misleading results.
• To achieve accurate results, secure container should be used which prevent
contamination of the sample. Therefore, resistant glass bottles or polyethylene
containers are recommended.
• While water sampling from a tab or metal lines and valves, allow sufficient flow of
water to wash out the system.
• After collecting sample, write all required data on a label that pasted in the container.
• If needed, store the sample in the refrigerator before taking it to the lab.
• A water sample needs to be shifted to the lab within a couple of days from collection.
• It is preferable to measure pH and EC immediately after sample collection.
Sometimes, diluted nitric acid treatment is required for preventing contamination
and microorganisms’ activity for a short time (APEC, 2022)

15. Precaution
• Before collecting soil water in the plastic bottle rinse it with distilled water and label it.
• Fill the sample bottle to within approximately 1 inch of the bottle top to facilitate mixing
in laboratory.
• Cap the sample bottle and place it in cooler.
• We can use the unfiltered water sample for the measurement of pH & electrical
conductivity, redox potential etc. but it needs to be filtered for the measurement of
nitrate, nitrite, ammonium, phosphate and metal elements.
• Ensure that a ‘representative’ sample is obtained, and possible cross
contamination from the surroundings should be understood and prevented.
• The samples should be analysed as soon as possible after collection because
chemical, biological changes can take place on standing.