Hydrology Iowa Units

53:119 Hydrology Fall 2012 UNITS AND MEASURES Fundamental measures (and their units in the SI and English systems) are: Length (m - meters; ft - feet) Mass (kg - kilograms) Time (s - seconds) Temperature (K - Kelvin; °F - degree Fahrenheit) Derived measures (and their SI and English equivalents) are: Area (m2 - square meters; ft2 - square feet) Volume (m3 - cubic meters; ft3 - cubic feet) Flow (m3 s-1 - cms; ft3 s-1 - cfs [volume per time]) Force (Newton (N) = 1 kg m s-2; lb - pound) Energy (Joule (J) = 1 kg m2 s-2 = 1 N m ; foot pound (ft lb) ) Power (Watt (W) = J s-1 or kg m2 s-3 ; horsepower (HP) ) Pressure (Pascal (Pa) = 1 N m-2 ; pounds per sq in (psi) - lb in-2 ) Prefixes used to construct decimal multiples of metric units 10-1 deci (d) 101 deca (da) 10-2 centi (c) 102 hecto (h) -3 milli (m) 10 103 kilo (k) 10-6 micro (µ) 106 mega (M) 10-9 nano (n) 109 giga (G) -12 pico (p) 1012 tera (T) 10 10-15 femto (f) 1015 peta (P) -18 atto (a) 10 1018 exa (E) Physical Constants: Standard Gravity Density of water (4°C) Specific Weight of Water (15°C) Kinematic Viscosity (15°C) Conversion formulas: °C = (5/9) (°F - 32) °F = (9/5) °C + 32 g = 9.807 m s-2 = 32.174 ft s-2 1000 kg m-3 = 1 g cm-3 62.4 lb ft-3 = 9800 N m-3 1.141x10-6 m2 s-1 = 1.217x10-5 ft2 s-1 K = °C + 273.15

Useful Conversions: • Length: 1 inch (in) = 2.540 cm 1 foot (ft) = 0.3048 m 1 mile (mi) = 5280 feet 1 nautical mile (nmi) = 1852 m 1 furlong = 110 fathoms = 660 feet = 1/8 miles • Mass - Weight - Force: 1 kg = 2.204623 pounds (lbs) 1 ton = 2000 lbs • Time 1 day = 86400 seconds • Area 1 acre (ac) = 43560 ft2 1 square mile (mi2) = 640 acres = 2.59 km2 1 lb = 4.448 N 1 metric ton = 1000 kg

• Volume 1 cubic centimeter (cc) = 1 milliliter (ml) 1 liter = 0.264179 gallons (gal) 1 gallon = 231 cubic inches 1 cubic foot = 7.481 gallons 1 acre-foot (ac-ft) = 43560 ft3 = (43560/86400) or .504167 cfs-days 1 cfs-day (cfsd) = 86400 ft3 = (86400/43560) or 1.983471 acre-feet • Flow 1 cms = 35.315 cfs 1 MGD (106