QUESTION 1: List at least five (5) sources of error in the measurement of precip
ID: 1765734 • Letter: Q
Question
QUESTION 1: List at least five (5) sources of error in the measurement of precipitation at a point. 2 Briefly discuss the advantages and disadvantages of estimating the average depth of rainfall on a catchment using arithmetic, Theissen, and isohyetal averages. Describe how you would distinguish between continuing losses and initial losses in the analysis of a storm event where you have a surface runoff hydrograph available. Discuss how you would estimate the design peak flow for an ungauged catchment in Eastern New South Wales. Infiltration losses during a storm event can be estimated using Horton's equation, the Green-Ampt equation and Philip's equation. Briefly discuss the conceptual differences between these alternative equations. Discuss reasons for selection of the depth at which the velocity measurement is made when a single point measurement technique is employed. Include in your discussion potential sources of systematic error which may invalidate the reason. Describe how you would distinguish between continuing losses and initial losses in analysis of a storm event where surface runoff occurs. Briefly discuss the importance of the three cell circulation pattern with respect to the location of desert areas on the Earth's surface. 1. 2. 3. 4. 5. 6. 8. 9. Describe briefly a conceptual model of the hydrological cycle. Include in your discussion reasons for conceptualisation of the hydrological cycle in the manner required for development of your model. 10. Briefly discuss the need for extrapolation of a rating curve at a gauging station. Include in your discussion an overview of how you would achieve the necessary extrapolation. 11. Briefly discuss the assumptions necessary for application of an at-site flood frequency analysis for estimation of the flood flow for a given exceedance probabilityExplanation / Answer
(1) Answer:- Sources of errors in the measurement of precipitation:-
(i) Some water is used to wet the surface of instrument.
(ii) Losses due to evaporation can also take place.
(iii) Error in measurement due to wind.
(iv) Dents in the collector and tube may also cause error.
(v) Some water is absorbed by the measuring stick.
(2) Answer:-
Advantage of arithematic mean method:- It is very easy to calculate rainfall by arithematic mean method.
Disadvantage of arithematic mean method:- By this method we can not calculate non uniform rainfall.This method is not useful in hilly area.
Advantage of Theissen polygon method:- This method is useful when rainfall stations are few compared to the size of the basin.
Disadvantage of Theissen polygon method:- This is more time consuming method.
Advantages of isohyetal method:- It is very useful in hilly and rugged area.
Disadvantage of isohyetal method:- For calculation of rainfall, we have to draw contours correctly.