As shown in figure 4, the number of macroinvertebrates at site E and F is generally less than around previous sites. This is a good indicator that the water quality is bad around site E due to the sewage problem that has been found there. Mayflies, stoneflies, caddisflies, and beetles are very intolerant to pollution. Their populations at sites E and F are drastically affected. The percentages of these intolerant macroinvertebrates to the total populations also goes down.
Midges are very tolerant to pollution.
They will live in non-polluted and polluted areas. Their populations go down at sites E and F but their percentages to the total populations goes up. This shows that there is a pollution problem at these sites because the macroinvertebrates that are sensitive to pollution are decreasing. Immediately, there is a problem with the water that only time and nature can heal. Nature almost always has a way of speeding things up.