1. Sornvara Kho-Udom
Geocience Period 4
Water Quality from Agricultural Runoff
Background Introduction:
Agricultural run-offs can be highly significant to the WQI of water sources like streams and
rivers. It can affect the cleanliness of water, and therefore affects the environment. Clean water is
necessary to all living things for survival. The purpose of this lab is to see the affects of agricultural run-
offs on water quality. In this lab, three water samples were collected from each of the three different
sources from the Chao Phraya River: upstream, agricultural run-off site, and downstream. The pH,
nitrates, phosphates, and turbidity were measured in each of the areas.
Clean water is important for a good health of all living things. No life would be able to survive
without water. It is one of the most important natural resources. Millions of people do not have access to
clean water, yet it is sometimes used carelessly. It is vital to monitor water quality over a period of time
in order to detect changes in the water's ecosystem
The Chao Phraya River is one of the most important sources of water in Thailand. It is used
every day by Thai people and is a necessity for transportation, agriculture, basic daily usages, etc.
PH is one of the most important factors of water quality. If the normal pH levels of a water
source are out of range, organisms living in it may not survive. Water contains hydrogen ions, H+ ions,
and hydroxide ions, OH-. The pH value is determined by the relative concentration of these two ions.
The pH level is at 7, it is neither basic nor acidic. It is at a neutral range, normal for drinking water.
A common form of phosphates is added by humans through agricultural wastes. Fertilizers
contain high levels of phosphates and can enter the water through runoff and soil erosion. Phosphates are
chemical compounds made from the elements phosphorous and oxygen; they are necessary for plant and
animal growth.
Turbidity is a measure of the water’s lack of clarity. If the water is cloudy it means that it has
high turbidity, whereas clear water means low turbidity. Many times, runoffs contain solids, which may
intensify turbidity of a river. High turbidity may be caused by soil erosion, waste discharge, urban runoff,
abundant bottom feeders (such as carp) that stir up bottom sediments, or algal growth. The presence of
suspended solids may cause color changes in water, from nearly white to red-brown, or to green from
algal blooms. The research question is: How does agricultural run-off affect the levels of pH, nitrates,
phosphates, and turbidity? The hypothesis is, if the agricultural run-off affects WQI levels, the source 2
will have the highest level of all the four tests.
Materials:
• Secchi Disk
• Nitrate Test Kit
• Phosphate Test Kit
• pH Indicator Test Strips
• Vials (4)
• Long-tail Boats
Procedure:
1. Go on a long tail boat in the Chao Phraya river and find an upstream source from what you are
going to be test (in this case, above the agricultural run-off)
2. Collect data for each of the following: pH, turbidity, phosphates, and nitrate levels
3. To collect pH, dip the pH indicator into the water and read accordingly
4. To collect turbidity, the Secchi disk lowered into the water until it can no longer be seen; the
depth (Secchi depth) is then recorded as a measure of the transparency of the water (inversely
related to turbidity).
5. [Refer to packet for phosphate and nitrate collection]

2. Data and Data Processing:
Table 1: pH, turbidity, phosphates, and nitrates levels from the three sources
Source 1 Source 2 Source 3
pH 6 6 6 7 6 6 7 6 6
Turbidity 45 45 45 45 45 45 43 42 43
Total phosphates 0 0 0 0 0 0 0 0 0
Nitrates .5 .5 .5 .25 .25 .25 .5 .5 .5
Table 2: Average of pH, turbidity, phosphates, and nitrates levels from the three sources
Source 1 Source 2 Source 3
pH 6 6.3 6.3
Turbidity 45 45 42.7
Total phosphates 0 0 0
Nitrates .5 .25 .5
Table 3: WQI for source 1
Test Parameter Test Results Q-Value Weighing Factor Total
pH 6 55 0.11 6.05
Turbidity 45 NTU 43 0.08 3.44
Total phosphates 0 100 0.10 10
Nitrates .5 mg/L 75 0.10
Table 4: WQI for source 2
Test Parameter Test Results Q-Value Weighing Factor Total
pH 6.3 60 0.11 6.6
Turbidity 45 NTU 43 0.08 3.44
Total phosphates 0 100 0.10 10
Nitrates .25 mg/L 90 0.10 9
Table 5: WQI for source 3

3. Test Parameter Test Results Q-Value Weighing Factor Total
pH 6.3 60 0.11 6.6
Turbidity 42.7 NTU 45 0.08 3.6
Total phosphates 0 100 0.10 10
Nitrates .5 mg/L 75 0.10 7.5
Figure 1: Different levels of each test in each of the three sources compared.
Figure 2: Phosphate levels from the three sources

4. Conclusion and Evalution:
Our hypothesis was not fully supported by the data for the most part. In fact, most of the data
contradicted to the hypothesis. It did not show any outstanding data or any major changes at all. In fact,
it stayed stable or had no signs of it at all. The phosphates data was the most surprising. As all the
phosphate levels from all the sources were zero. This is surprising because the phosphate levels in the
agricultural run-off should be high, because it is a powerful source of phosphates. Also, the turbidity was
pretty stable throughout the whole data collected, upsteam, at the agricultural run-off, and downsteam .
The levels should be higher from the waste produced. But contradictingly, the turbidity and nitrate levels
got lower downstream. The pH did increase as expected, from the source and continued downstream.
The overall health of the water is considered at a normal range.
There were many possible sources of erros. Firstly, the tests were rushed, because we had a
limited amount of time on the boats. The time frame where we measured the results may not be equal.
There should be more time to conducted the tests. Also, the equipment used was the same one and may
have been affected by previous samples because there was no source of clean fresh water to clean the
equipments. Furthermore, there was a factory above the source, which may have affectedthe pH,
phosphate and nitrate levels. That are riser than normal than the upstream.