Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Paper: National Exams — 98-Civ-A5 Hydraulic Engineering, December 2013 · 3 hours, closed book (one 8.5×11 aid sheet). Six questions; any five constitute a complete paper — all six are solved here as a study resource. All parts of a question are of equal value; ‘cms’ = m³/s.
Reference texts. Mays, Water Resources Engineering, 3rd ed. (pipe systems, valves, network analysis); Chow, Open-Channel Hydraulics (Manning uniform flow, gutter flow); Crowe, Elger & Roberson, Engineering Fluid Mechanics (laminar film flow, energy/continuity). Exam-supplied relations used throughout: Hazen–Williams $Q=0.278\,C\,D^{2.63}\,S^{0.54}$ with $S=h_f/L$ (SI), Manning $Q=\tfrac{1}{n}A\,R^{2/3}\,S^{1/2}$, Darcy–Weisbach, and total dynamic head $\text{TDH}=H_s+H_f$. Unless stated, local losses and velocity head are neglected and water has $\rho=1000\ \text{kg/m}^3$, $\nu=1.31\times10^{-6}\ \text{m}^2/\text{s}$.
The Hazen–Williams relation is used in inverted form to get the friction loss carried by a known pipe discharge $Q$ (SI, $Q$ in m³/s):
$$h_f = L\left(\dfrac{Q}{0.278\,C\,D^{2.63}}\right)^{1/0.54}.$$