What is meant by the term Alkalinity when discussing a raw water? Why is the alkalinity of a raw water important when discussing possible treatment processes? (ii) A sample of raw water collected in the field had a pH 6.8. On arrival to the laboratory for analysis, the pH was measured at 7.5. Give a possible natural reason (e.g. excluding contamination) for this change in pH of the sample. What is 'good practice' model which arises from this incidence? b) A well is 0.2 m in diameter and pumps from an unconfined aquifer 30 m deep at an equilibrium (steady-state) rate of 1000 m3 per day. The observation wells are located at distances 50 and 100 m, and they have been drawn down by 0.2 and 0.3 m, respectively. Determine: (i) the coefficient of permeability of the aquifer (ii) the estimated drawdown at the well?