Final answer:
The slope of a line represents the rate of change and the y-intercept represents the starting point.
Step-by-step explanation:
The slope of a line represents the rate of change between the independent and dependent variables. It tells us how the dependent variable changes for every one-unit increase in the independent variable, on average. In this case, the slope represents the rate of increase in water level per day. For example, if the slope is 2, it means that the water level increases by 2 units every day.
The y-intercept is the point where the line intersects the vertical, y-axis. In this case, the y-intercept represents the beginning water level. For example, if the y-intercept is 5, it means that the water level starts at 5 units.