CIVL 4330/6330 Hydrology 2017 Assignment 1 Due date: 1pm Friday 31 March 2017 A single submission from a group of two students is encouraged. Hand in well organized tidy solutions. You do not need to type. Indeed you are encouraged to submit hand-written work. Properly annotate graphs and spreadsheets so there is no need to second guess what you did. It is unprofessional to submit sloppy difficult-to-follow work. Such work will not be marked. Each question has an allocated mark. Marks will be awarded for correctness, clarity and comprehensiveness of answers and may be deducted for unacceptable presentation. Questions marked as OPTIONAL will not be marked. Nonetheless you are strongly encouraged to attempt them. The map in Figure 1 displays the catchment for the Karuah River at Booral. This assignment will examine rainfall and meteorological data for this catchment. Note: the map scale can be obtained from the fact that the distance between the Stroud and Ward's River raingauges is 20 km. All the files for this assignment can be found in the zip file, Ass1_Files.zip, in the Blackboard hydrology strand assignment 1 folder. Answer the following questions: 1. (40 marks) Compute the catchment rainfall over the Karuah catchment for the 3-day period associated with the March 1978 flood using: i) an arithmetic average of rain gage data ( 5 marks) ii) Thiessen polygons (15 marks) iii) an isohyetal map (15 marks) The following 3-day totals were recorded: Raingauge 3-day rainfall depth (mm) Craven 268 Chichester 406 Walleroo 180 Stroud 274 Comment on the accuracy of the methods used (5 marks) Hint: To work out areas draw Thiessen polygons and isohyets on the bitmap file karuahMap.bmp using Microsoft PAINT (or equivalent) and then run the program MAP.EXE to digitize the areas. 2. (20 marks) The zip file contains radiosonde data from Williamtown AMO on the Sunday 24th Feb 2002. Calculate the depth of precipitable water in the atmosphere from this data (10 marks). What is the environmental lapse rate (10 marks)?3. (OPTIONAL) The file stroudAnnMax9amDailyRainfall.xls has the annual maximum 9am daily rainfall from 1889 to 1998. Note that annual maximum 9am daily rainfall underestimates the annual maximum 24 hour rainfall because it is collected between fixed times each day. Before you start this question correct for this bias by multiplying the 9am data by 1.1 (there is a rigorous statistical derivation for this correction factor). Do the following: i) Plot the data on a log-normal probability plot using EXCEL and the median plotting position (10 marks). ii) Fit a log Pearson III distribution to the Stroud annual maximum 24-hr rainfall data. Compute the AEP 1 in 10, 50 and 100 24-hour rainfall depths. Do this by computing in EXCEL the mean, standard deviation and skew of the logarithm of the 24-hour annual maximum data (10 marks). iii) Plot the AEP 1 in 2, 5, 10, 50 and 100 24-hour rainfall depths calculated in part (ii) on the log-normal probability plot. Comment on the fit (10 marks). 4. (OPTIONAL) Determine the AEP 1 in 10, 50 and 100, 24 hour duration storm for Stroud using the regionalized ARR (Australian Rainfall and Runoff) IFD2013 (intensity-frequencyduration) procedure. Use the following latitude and longitude for Stroud: 32.4000° S, 151.9667° E Comment on the differences between your answer in question 3 and the ARR IFD2013 values. 5. (15 marks) Determine the 4-hour duration probable maximum precipitation (PMP) for a 50 km2 catchment with smooth terrain centred around Stroud. Determine the temporal pattern for the storm? Present the temporal pattern as a bar graph of rainfall depths vs time over 30- minute intervals.Figure 1. Map of Karuah catchment