Streams are one of the major sources of freshwater all over the world. The hill streams of Western Ghats are the source for all the major perennial rivers of Southern India. The streams originating from the Nilgiris district of the Western Ghats confluence in either the Moyar or Kaveri basins in their eastern slopes. These streams have become vulnerable with an increase of human disturbance
and pollution. Freshwater macroinvertebrates are widely used as good bioindicators of freshwater systems. Studies carried out around the world have shown that with increased pollution and change in water quality, the structure and diversity of freshwater macroinvertebrates changes. Thirty streams covering different habitat types were sampled using kick-net and dip-net methods. Each stream was classified as either disturbed or less disturbed taking into consideration the different disturbances present at each stream. Results indicate that sites with greater disturbance had a lower diversity, biological monitoring working party (BMWP), Ephemeroptera, Plecoptera, and Trichoptera (EPT) and saprobic scores while having higher total dissolved solids (TDS) values, with less disturbed sites showing contrasting results. Parasites and high tolerance families were seen to be higher in disturbed sites, while sensitive families such as Ephemeroptera, Plecoptera and Trichoptera were seen to have high abundance in less disturbed sites. This study shows that freshwater macroinvertebrate communities change across a disturbance gradient with poor water quality. Such disturbances can cause a drop in local biodiversity affecting the entire freshwater ecosystem and the livelihoods dependent on them.