runoff

Question 1

overland flow

Answer 1

water reaching stream while traveling above ground

Question 2

Subsurface flow

Answer 2

water reaching stream through shallow soil & underlying rock layer
-Shallow subsurface flow SSSF = upper soil layer
-GW flow (GWF) = deeper soil & rock layer

Question 3

HOF: Infiltration-excess overland flow

Answer 3

occurs when rainfall rate exceeds soil infiltration rate (more likely in clay soil = slower f(t))

Question 4

rainfall excess

Answer 4

rainfall neither retained on land surface nor infiltrated into soil
Excess rainfall = observed rainfall- hydrologic abstraction

Question 5

HOF occurence

Answer 5

road surface & impermeable areas
hydrophobic soils
trampled & crusted soils
Frozen ground
Low-permeability soils

Question 6

SOF : saturation-excess overland flow

Answer 6

when soil is fully saturated and no space for additional water infiltration, any additional precipitation becomes SOF
-mainly occurs on topographic low & near streams (water table reaching surface)

Question 7

Return flow

Answer 7

Subsurface water pushed towards surface. soil water properties affect water quality of return flow.

Question 8

Variable source area

Answer 8

expanding/shrinking saturated area during/after rainfall event

Question 9

Assessing landscape overland flow

Answer 9

consider seasonality AND storm fluctuation
more humid with less rainfall intensity = SOF
-more arid with high rainfall intensity = HOF

Question 10

matrix flow

Answer 10

water moving through small soil pores

Question 11

subsurface fill and spill mechanism

Answer 11

water spill from one depression to another at soil-bedrock interface

Question 12

macropore flow

Answer 12

water moving through larger soil pores

Question 13

pipeflow

Answer 13

water moving through large soil cavities, bypassing soil matrix.
-frequent in organic soils

Question 14

GW flow

Answer 14

water move below water table in soil/ rock

Question 15

types of subsurface flow

Answer 15

matrix flow
fill and spill mechanism
pipeflow
macropore flow
GW flow

Question 16

Shallow subsurface stormflow development

Answer 16

1. at start, percolation occurs vertically
2. soil moisture increase, some water bypassing to depth
3. water table rise towards soil surface
4. before water table reach surface, hydraulic condition change -> Lateral hydraulic conductivity > vertical hydraulic conductivity

Question 17

perched SSSF development

Answer 17

1.Same as SSSF but, percolation reaches impeding layer and saturation occurs.
2. perched water table rise and before reaching surface hydraulic conductivity changes (lateral>vertical)

Question 18

subsurface fill & spill development

Answer 18

impermeable boundaries restricting water percolation causes bedrock hollow to fill and spill -> forming continuous flow

Question 19

Macropore flow characteristics

Answer 19

-depends on pore size distribution & interconnection of pores overtime, forming a network
-lots of macropores are biopores
-preferential flow in macropores
-permeable walls -> when saturated, lateral infiltration occur via macropore flow

Question 20

preferential runoff pathway definition

Answer 20

uneven and often rapid movement of water & solutes through soil at a faster than normal matrix flow, so that a small fraction of the media participates in most of the flow

Question 21

preferential flow occurence

Answer 21

-distinctive structure of soil where water flows only under gravity
-areas with higher permeability than surrounding soil matrix
- occurs with: Macropore, pipe and matrix flow (perched SSSF, fill & spill)

Question 22

impact of runoff on water quality

Answer 22

-influence base cation/anion concentration as water pick up ions by traveling through soil
-large effect on nutrient & sediment flushing and reaching streams

Question 23

spatiotemporal variability of runoff flows

Answer 23

-can have multiple overland & subsurface flow types at same time
-antecedent wetness conditions are IMP

Question 24

role of watershed characteristics in runoff flow

Answer 24

forest: high evapotranspi, low surface runoff, higher subsurface flow/infiltration
Degraded land: lower evapotranspi, higher surface runoff, medium subsurface flow/infiltration