HydroCOMP - Hydrologic Calculations using Mathcad
James B Hart, Forestry Department, Michigan State University

This non-commercial public service site previously used the name -----CAD instead of HydroCOMP. The name was changed at the request of a tradename owner.  Numerous page links must be edited before the pages can be reposted. This is a temporary removal from the public domain until all files can be modified to the new name HydroCOMP.  If you have need for the contents below in HTML format or MathCAD format contact me.


Written in MATHCAD 11 Enterprise Edition by Mathsoft and saved as HTML & MCD files.
Contact hart@msu.edu or (517) 355-9528 for additional information.

Below are topic and links to MathCad computation sheets and HTML documents useful in hydrology computations intended for use in public education, for computations by hydrologists, and in hydrologic research. Example calculations from cited references are shown when available for verification of correct computation. 
James B. Hart is solely responsible for the information on these sheets. User are advised to read cited references to determine limitations and proper use of information.
These works may be cited as personal communication James Hart, or as a URL reference.
UNITS, CONVERSIONS, SIGNIFICANT DIGITS, GLOSSARIES
American Society of Agronomy Units and Conversions 
HTML
More units to use
MCD
Temperature scales and conversions
MCD
Significant Digits Information
HTML
Soil Science Society of America Glossary of soil science terms HTML
DAYS, DATES AND DAY LENGTH CALCULATIONS
Day number from year, month and day
(Also Days between two dates and Day of Year)
MCD
Day length calculation from Date (day and month) and Latitude
MCD
CLIMATOLOGICAL AND METEROLOGICAL COMPUTATIONS 
Air saturated Vapor Pressure (es) calculation from Temperature (Lee 1980)
MCD
Dew Point temperature from air temperature and relative humidity (Cuenca, 1989)
MCD
PRECIPITATION AND SNOW HYDROLOGY
Snow Density, Water Equivalent, Ice Content and Quality Calculations
developed, pending
Arithmetric, Thiessen & Isohyetal areal precipitaiton from vicinity rainfall points 
future development
Reciprical average mean precipitation from vicinity rainfall points 
future development
SOIL WATER POTENTIAL 
MathCad Units for Water Potential 
MCD
Saturated water potential from elevation, electrical conductivity and water depth 
in development
Unsaturated water potential from elevation, conductivity and matric potential 
in development
SOIL SAMPLE WEIGHT-VOLUME-DENSITY RELATIONSHIPS - SOIL ARCHITECTURE 
Volume, Weight, Porosity,Density and Concentration Relationships of a Typical Loam Soil
HTML
WATER RELATIONSHIPS OF POROUS MEDIA (SOIL SAMPLES)
Water concentration by weight, volume and depth 
in development
Water content by weight, volume and depth 
in development
Field Capacity, Wilting Point and Available Water from Sand, Clay and Soil Org. Matter
MCD
Rawls et al. 1982
Generalized soil-water characteristics and curve from texture per Saxton (1986)
MCD
Generalized soil hydraulic conductivity from texture & Theta (or Potential) per Saxton 86
MCD
WATER COMPUTATIONS OF SOIL HORIZONS AND PROFILES
Soil Weight (Dry) Calculation from Volume (or Area & Thickness) and BD
in development
Soil Water Content from %water, Thickness and Course Fragment % 
in development
AWC Available Water Capacity (storage) for a soil profile from texture, thickness, and %course Fragments
in development
EVAPORATION AND POTENTIAL EVAPOTRANSPIRATION COMPUTATIONS
Lake evaporation estimation from Class A pan evaporation using "pan coeficient"
MCD
Monthly PET from Latitude, MAT, Month and Mean Mo Temp per Thornthwaite (1948) 
MCD
Daily PET from Latitude, Month, Day and Daily Temperature per Hamen (1961)
MCD
Modified Pennman PET per Kinkaid and Herrman (1974)
MCD
Penman-Monteith PET per Monteith (1965)
future development
Daily PET, PT and PE per Shuttleworth & Wallace (1985)
in development
Daily PET, PT and PE per Hudson 1995 
(simplified Shuttleworth & Wallace, 1985)
in development
WATER BALANCES OF VADOSE ZONES (ROOT ZONES)
Water balance computations for a root zone layer using timesteps
MCD
Thornthwaite Monthly & Annual Water Balance from Georgia PET, P, AWC and initial soil water (Example from Hewlett & Nutter, 1969) 
MCD
INFILTRATION INTO SOILS
Green-Amp infiltration
developed, pending
Horton infiltration
in development
Richards infiltration 
in development
UNSATURATED ZONE (VADOSE) WATER COMPUTATIONS
Percolation of water out of a soil layer per Raes (1988)
MCD
SATURATED ZONE (GROUNDWATER) WATER COMPUTATIONS
Capillary Rise per Scott 2000
MCD
Darcy's Law and Saturated Latral Flow Calculations Scott 2000 
in development
Darcy's Law and lateral groundwater movement across a sandy landscape 
developed, pending
Unsaturated Piezometric Surface Gradient and Direction from 4+ wells
in development
Confined Piezometric Surface Gradient and Direction from 3 wells
in development
Detention storage capacity from architecture and thickness of soil layers 
in development
Unconfined aquifer gradient & direction from xyz coordinates in 4 or more wells 
developed, pending
STREAM HYDROGRAPHS
Unit Stream hydrograph development using a spline function 
developed, pending
ROOT ZONE HYDROGRAPHS
Precipitation hydrograph of a terrestrial ecosystem
Actual Evapotranspiration hydrograph of a terrestrial ecosystem (1 layer root zone)
Available water hydrograph of a terrestrial ecosystem (1 layer root zone)
Leaching hydrograph of a terrestrial ecosystem (1 layer root zone)