Chapter XV

155. Waste of Water, Particularly in the City of New York 196
156. Division of Daily Consumption in the City of New York 197
157. Daily Domestic Consumption 198
158. Incurable and Curable Wastes 199
159. Needless and Incurable Waste in City of New York 200
160. Increase in Population 200
161. Sources of Public Water-supplies 202
162. Rain-gauges and their Records 204
163. Elements of Annual and Monthly Rainfall 204
164. Hourly or Less Rates of Rainfall 207
165. Extent of Heavy Rain-storms 207
166. Provision for Low Rainfall Years 208
167. Available Portion of Rainfall or Run-off of Watersheds 209
168. Run-off of Sudbury Watershed 211
169. Run-off of Croton Watershed 211
170. Evaporation from Reservoirs 213
171. Evaporation from the Earth’s Surface 215

CHAPTER XVI.
172. Application of Fitzgerald’s Results to the Croton Watershed 216
173. The Capacity of the Croton Watershed 217
174. Necessary Storage for New York Supply to Compensate
for Deficiency 218
175. No Exact Rule for Storage Capacity 220
176. The Color of Water 221
177. Stripping Reservoir Sites 222
178. Average Depth of Reservoirs should be as
Great as Practicable 224
179. Overturn of Contents of Reservoirs Due to
Seasonal Changes of Temperature 224
180. The Construction of Reservoirs 225
181. Gate-houses, and Pipe-lines in Embankments 229
182. High Masonry Dams 230

CHAPTER XVII.
183. Gravity Supplies 234
184. Masonry Conduits 234
185. Metal Conduits 236
186. General Formula for Discharge of Conduits—Chezy’s Formula 237
187. Kutter’s Formula 239
188. Hydraulic Gradient 241
189. Flow of Water in Large Masonry Conduits 244
190. Flow of Water through Large Closed Pipes 245
191. Change of Hydraulic Gradient by Changing Diameter of Pip 250
192. Control of Flow by Gates at Upper End of Pipe-line 251
193. Flow in Old and New Cast-iron Pipes—Tubercles 251
194. Timber-stave Pipes 253

CHAPTER XVIII.
195. Pumping and Pumps 254
196. Resistances of Pumps and Main—Dynamic Head 258
197. Duty of Pumping-engines 260
198. Data to be Observed in Pumping-engine Tests 261
199. Basis of Computations for Duty 262
200. Heat-units and Ash in 100 Pounds of Coal,
and Amount of Work Equivalent to a Heat-unit 262
201. Three Methods of Estimating Duty 265
202. Trial Test and Duty of Allis Pumping-engine 265
203. Conditions Affecting Duty of Pumping-engines 266
204. Speeds and Duties of Modern Pumping-engines 266

CHAPTER XIX.
205. Distributing-reservoirs and their Capacities 267
206. System of Distributing Mains and Pipes 268
207. Diameters of and Velocities in Distributing Mains and Pipes 269
208. Required Pressures in Mains and Pipes 270
209. Fire-hydrants 270
210. Elements of Distributing Systems 270