Ren R 110 - Hydrology

Hydrology

The study of water in all forms, processes and reactions across Earth

Drainage Basin

Funnel that collects water and channels it to a single point, caused by topographic barriers (eg: mountains)

Watershed

Area that collects and discharges run off through a streampoint

Sectoral Water allocations

Max amount of water that has been granted for us in a particular sector

Watershed protection (and examples)

Managing withdrawals and the influences of humans on watersheds

Eg: Minimizing sedimentation, preventing debris from entering, maintaining aquatic and terrestrial habitats, complying with the water act

What are the zones of aeration and saturation

Zone of aeration: Above the water table, where water and air both occur

Zone of saturation: Below the water table where there is little air, and mainly water

What is the formula for water content in soil by mass percent

percent water content = (Mass wet - Mass dry)/Mass dry * 100

How do you convert between mass of water and volume of water?

They’re the same

What is the formula for water percent by volume?

Volume water/volume of soil * 100

Bulk Density

Soil mass per unit volume of soil, giving information about how much water and air is present

Bulk density decreases as the volume of air decreases

What is the formula for bulk density?

Dry mass of soil/total volume of soil

What is the formula for water content by volume?

Water content by mass * bulk density

What is the mixtures formula?

X = Sum of(weight * values)/ Sum of weight

What is the formula for calculating total rain fall from a rain gauge?

total rain = water volume/area

Volume = pi(radius small part)² * height of water (converted from mm)

Area = pi(radius of top)²

Watershed

Land/Area that channels rain and snowmelt into rivers/streams eventually leading to outflow points

What are the 2 methods for calculating rainfall using rainguages?

Average the values from the rain guages

Isohyet method (dividing lines of equal precipitation)

What is the isohyet formula?

Sum of (AREAi*RAINFALLi/total area)

Snow gauge and snow stake

Snow gauge: Like rain gauge but for snow

Snow stake: Measures the depth of the snow

What is the snow water equivalent, what are the steps

Relationship between snow and water

1. Find snow volume (pir²h)

2. Calculate the density of snow (Mass/volume)

3. Use the density number * corer depth to get amount of water

Discharge (Q)

Volume of water flowing through a given area at any time (including the stuff in it)

Discharge (Q) formula (in m³^-s)

area * velocity

Stream velocity formula

Distance/time

How do slope, depth and roughness affect stream velocity

Slope increase - velocity increase

Depth increase - velocity decrease

Roughness increase - velocity decrease

Width formulas for stream

width = upper-lower/2

Edge width = bigger-smaller/2

Total discharge (Q) formula

Sum of (avg velocityi*widthi*averagedepthi)

Storm hydrography

Measure of discharge (Q) in response to precipitation over days

Rising Limb

Prior to discharge peak

Falling limb

After peak discharge

Baseflow

Steady addition to stream from groundwater

Peak discharge

Point of greatest discharge

Time lag

Time from peak rainfall to peak discharge

Banfull discharge

Point where flooding will occur

What can affect peak discharge? how? (4 factors)

Size of drainage basin

• Small - lower peak

• Large - higher peak

Vegetation

• Bare - higher peak

• Forest - lower peak

Valley side steepness

• Steep - higher peak

• Gentle - Lower peak

Soil Type

• Impermeable - higher peak

• Permeable - Lower peak

Paired Watersheds

Two watersheds that are close together, with same size, aspect, vegetation, and rainfall to compare Q

What are the steps for paired watershed calculations

1. Determine the control (x) and the treatment (y)

2. Calculate the flows and make a regression equation for the two of them

3. Apply treatment to y

4. Calculate expected value of y with the measured value of x in the regression equation

5. Take the difference of observed-expected

6. Take the average difference across the years if applicable

Risk

Potential of gaining or losing something

Return period

Likelihood of an event happening, balanced with the cost of adding extra precautions

Return period (and formula)

Probability of an event happening based on the historic data

Tr = N (time interval)/ n (how many times the event is seen)

Formulas for the probability of an event happening

p = 1/tr

p^n = (1-p)^n where n=number of years

Sediment yield

Affects the water quality and soil erosion

Manual samplers

Collection jars raised and lowered in the river to collect sediment

Sediment concentration formula

SSC = Mass (weight of sediment)/Volume of water

Sediment yield Formula

Sediment yield = Q (discharge) * SSC (sediment concetration)

Concentration formula

CaMa +CbMb = CtMt