The water quality of the Hilla River, located in Iraq, has been varying due to the presence of different illegal point and non-points sources along the river stream. This study highlighted the carbonaceous biological oxygen demand (CBOD) and dissolved oxygen (DO) levels for safe usage by applying the river and stream water quality model called QUẠL2K model, depending on the hydraulic and water quality data collected along 6.8 km passing through the main city (Hilla City) on October 2022 (low flow season) and January 2023 (high flow season). The modeling results showed that the simulated predictions are in good agreement with field data. The outputs revealed the two parameters (CBOD and DO) ranged between (1.425–3.075) mg/L and (9.5–10.65) mg/L, respectively, during low flow season and between (0.745–2) mg/L and (9.5–10.5) mg/L, respectively, during high flow season. The river CBOD levels along the river follow same pattern during the high and low flow seasons, but the DO levels behaved inversely. However, both parameters were within the acceptable limits. Thus, the river health can be considered good for basic human usage.
This investigation of the biodiversity of copepods was carried out in the Hilla River. From January 2021 to December 2021, monthly samples of water and copepods were taken at three different locations in the river for this investigation. Water’s temperature, turbidity, pH, salinity, dissolved oxygen, biological oxygen demand, total hardness, nitrate, and phosphate are some of the physical and chemical characteristics taken into account. A study was undertaken using biological indicators such the Shanon-Weiner index, Species Uniformity Index, and Species Richness Index. There were 24 copepod taxonomic units found. Copepoda had a maximum density of 1453 ind/m3 in April and a lowest density of 80 ind/m3 in February. The statistical study’ findings revealed a statistically significant positive association between density, all of pH, BOD5, Nitrate, and Phosphate, as well as a statistically significant negative correlation with each of dissolved oxygen and total hardness. The Shanon-Weiner index recorded its greatest value in May, 3.33 bits/ind, and its lowest value in December, 0.08 bits/ind. The greatest value of the Species Uniformity Index (E) was 0.99 in March, while the lowest values of 0.1 were reported in July. Species homogeneity index and each of Turbidity have a substantial negative association and a strong positive connection, respectively. The Species Richness Index reached its greatest point in April (6.13), while it reached its lowest point in January (1.46). According to the statistical study, there is a strong positive association between Index values and a strong negative correlation with overall hardness.
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