Spatio-temporal changes of water quality variables in a highly disturbed river

Quality of river varies widely depending on the land use in the catchment and environmentalfactors. Many rivers in developing countries are unhealthy because they contain harmful physical, chemicaland biological agents. Zanjanrud River, located in Zanjan Province, Iran, where recently faced humanintervention needs a regular monitoring from upstream to downstream for sustainable management. Hence,the current study aimed to assess spatial and temporal variations of pollutant in Zanjanrud River in differentstations from headstream to tail of the river. To achieve this goal, semi-monthly samples were collectedfrom October 2015 to Jun 2016 at 5 stations along the river. The physicochemical variables were monitoredand analysed using two-way analysis of variance. The results showed the highest values of suspended anddissolved solids and total solids (220.13±5.57, 641.6±39.63 and 793.6±34.5mg/L respectively) were at thetail site in low-flow period. Nitrate-nitrogen and nitrate were also highest (5.39±02.44 and 23.90±10.85mg/L) at the middle of the river where was vicinity to farm lands. The values of pH and dissolved oxygenranged from 6 to 8.15 and 0.5 to 4mg/L respectively with the highest values in high-flow period at mostof the study sites. The maximum and minimum values of electrical conductivity (1439 and 256μs/cm)were recorded at tail site and headstream site respectively. Hardness had an increasing trend from upstreamto downstream (189.60±53.53 to 515.83±64.77mg/L). Phosphorus was also lowest (0.09±0.04mg/L) atupstream. Results illustrated the high degree of pollutant in studied river. So, an effective management oferosion, domestic waste and agricultural activities in watershed is highly recommended.

Keywords:

Hydrologic behaviour , Non-point source pollution , Physicochemical variables , Quality indicators , River management