Statement 1: We can use water instead of mercury to construct a barometer for measuring the atmospheric pressure.
Statement 2: We do not use water in a barometer because it will be very inconvenient to use.
Both the statements are correct.
A barometer quantifies pressure by balancing the pressure force with the weight of the liquid column. We can use any liquid to construct a barometer but we use mercury because of its high density. A denser/heavier liquid means shorter height of the column to balance the pressure. For example the density of water is 13.6 times smaller than that of mercury, that means we would require a 13.6 times taller column of water than that of mercury to measure same pressure difference. Thus obviously water will be very inconvenient to use.