| Critical Parameter-wise Water Quality Trend in India (During 1986-2000) | ||
| Critical Parameter | Range | Percent of Observations |
| BOD | < 3 mg/l | 53-73% during 1986 to 2000. Maximum observations 73% during 1988, during 2000 decreased to 59% |
| 3-6 mg/l | 20-25% during 1986 to 1993. Maximum observations 28% during 1995. | |
| > 6 mg/l | 5-20% during 1986 to 1995. Maximum observations 20% during 1996. During 2000 decreased to 16%. | |
| Total Coliform | < 500 MPN/100 ml. | 36-50% during 1986 to 1998. Observations increased to 63% in 1999 & further decreased to 46%, |
| 500-5000 MPN/100 ml. | 31-40% during 1986 to 2000. Maximum observations 40% in 1986 decreased to 32% in year 2000. | |
| > 5000 MPN/100 ml. | 9-30% during 1986 to 2000. Maximum observations (30%) during 1989 decreased to 9% in 1999, increased to 20% in 2000. | |
| Faecal Coliform | < 500 MPN/100 ml. | 37-67% during 1986 to 2000. Maximum observations 67% during 1998, decreased to 48% in 1999 again increased to 55% in 2000. |
| 500-5000 MPN/100 ml. | 27-37% during 1986 to 2000. Maximum observations in 1993, decreased to 23% during year 2000. | |
| > 5000 MPN/100 ml. | 7-33% during 1986 to 2000. Maximum observations in 1990, decreased to 7% during 1998 again increased to 19% during year 2000. | |
