TEST 2 HYDRAULICS NOVEMBER 2009-MARCH 2010.doc

BEC 208 HYDRAULICS AND HYDROLOGYTEST NO.2INSTRUCTIONS : TIME: 2.5 HOURSAnswer ALL questions.QUESTION 11a)List out four (4) importance of the study of engineering hydrology in solving any water related problem.(4 marks)1b)With the aid of a diagram, illustrate the complete process of hydrological cycle on earth. Explain briefly on each process and its components. (15 marks)1c)Briefly explain four (3) factors affecting infiltration process. (6 marks)(Total = 25 marks)QUESTION 22a)For a given month, a 130 ha lake has 0.43 m3/s of inflow, 0.37 m3/s of outflow, and the total storage increase of 1.97 ha-m. A USGS gauge next to the lake recorded a total of 5.3 cm precipitation for the lake for the month. Assuming that infiltration loss is insignificant for the lake, determine the evaporation loss, in cm over the lake for the month.(1 ha = 10 000 km2)(15 marks)2b)At a particular time, the storage in a river reach is 120 x 103 m3. At that time, the inflow into the reach is 10 m3/s and the outflow is 15 m3/s. After two hours, the inflow and the outflow are 18 m3/s and 25 m3/s respectively. Determine the change in storage during two hours period and the storage volume after two hours. (10 marks)(Total = 25 marks)QUESTION 33a)One of the monthly recorded rain gauges one particular catchment develops a fault in a certain month when the other three gauges recorded precipitation of 37 mm, 43 mm, and 51 mm respectively. If the average annual precipitation amounts of these three gauges are 726 mm, 752 mm and 840 mm respectively and of the faulty gauges is 694 mm, estimate the missing monthly precipitation at this faulty gauge.(5 marks)3b)Using the data in the Table Q3 (b) given, estimate the precipitation depth in cm that has fallen on the estimated watershed.Table Q3 (b)StationObserved Rainfall(mm)Polygon Thiessen Area(km2)A277528 B208387C152916D1241505E91758(10 marks)3c)Lines delineating a particular measurement are drawn within a watershed. Precipitation data and the area in between each isohyet are shown in the table below :-Isohyetal line (cm)Area (cme)16 13 9513 1012810 7 1207 4 1784 1 79(10 marks)(Total = 25 marks)QUESTION 44a)The rainfall intensity in the 50 ha of a catchment area is given in the table below. If the volume of surface runoff is 30 000 m3, estimate the f-index for the catchment area.Time (hour)Rainfall Intensity (mm/hour)1 521033842551365(10 marks)4b)A river discharge was measured using a standard current meter. The data of river measurement is listed in the table and figure below (Table Q4(b) and Figure Q4(b). Determine the discharge of the river using mean section method if the equation of the current meter is:-V = 0.51 Ns + 0.03 Table Q4 (b)Sub-Section1234Rotation N at 0.6d39.0058.0070.0060.00Observation time (s)100.00120.00180.00120.008 m1238 m04+ 46 m m+ 44 m m+ 50 m+ 45 m mmm5 m5 m8 mFigure Q4 (15 marks)(Total = 25 marks)APPENDIX 1Important Formulas Discharge,Discharge per unit width, q= By Manning,Velocity, V = Discharge, Q = Hydraulic radius, R = Froude Number, Fr= Critical Depth, DC :a. For rectangular channel,Dc= b. For non-rectangular channel, For hydraulic jump, D2 = Head loss, hj = Fr= Pw = g