Stream Flow

Question 1

Why is stream flow important?

Answer 1

-high flows are important to estimate flood discharge
-low flows important to understand water requirements, min flow to support navigation, recreation, and aquatic life
Flow is represented by change in discharge with time

Question 2

Factors affecting hydrographs

Answer 2

-Precipitation characteristics,
rainfall intensity and pattern
type, size and direction of storm movement

-watershed characteristics
Size and shape of drainage area
Soil type and land use
Storage in watershed

Question 3

Direct runoff - rapid response

Answer 3

-generated by precipitation
-all overland flow and precipitation directly on stream
-main contributor to peak discharge

Question 4

Indirect runoff - slow response

Answer 4

-subsurface runoff generated by precipitation
-interflow
-base flow

Question 5

Interflow -moderate response

Answer 5

-slower than direct runoff
-infiltrated water that moves laterally in subsurface until reaching channel
-consists of quick interflow which contributes to direct runoff
-delayed interflow which contributes to base flow

Question 6

Base flow - slow response

Answer 6

-groundwater runoff and delayed groundwater runoff contributes to channel
-extremely slow

Question 7

Channel precipitation

Answer 7

-originates from rainfall on the stream and water bodies connected
-average precipitation multiplied by area covered by water surface

Question 8

Major components of stream flow

Answer 8

-base flow
-direct runoff

Question 9

Minor components of stream flow

Answer 9

-interflow
-channel precipitation

Question 10

Streamflow measurement

Answer 10

-direct method
Discharge measure with velocity area method. Taking multiple measurements across stream and mtiltpliying them by the area of the cross section

-indirect method
Establishes a rating curve based on the relationship between the water storage and the discharge

Question 11

Rising limb

Answer 11

-represents increase in discharge due to the gradual building up of storage in channels
-the climate factors generally control the rising limb

Question 12

Crest of hydrograph

Answer 12

-where the peak flow occurs due to the runoff from various parts of the watershed contributing to the max amount of flow at the outlet

Question 13

Recession limb of hydrograph

Answer 13

-extends from the point of inflection at the end of the crest to the start of natural groundwater flow
-represents withdrawal of water from the storage built up in the basin
-starting condition represents the condition of max storage
-determined by catchment characteristics

Question 14

Hydrograph in a humid climate has what characteristics?

Answer 14

-continuous
-not smooth
-high infiltration
-spikes caused by rainstorm

Question 15

Hydrograph in a arid climate has what characteristics?

Answer 15

-not continuous
-not smooth
-mostly direct runoff
-long period where channel is dry
-little infiltration

Question 16

Snowfed river hydrograph has what characteristics?

Answer 16

-continuous
-relatively smooth due to steady release from the snowpack
-most of base flow is due to snowmelt

Question 17

Hydrograph analysis serves what purpose?

Answer 17

-examine a storm hydrograph and determine the relative contribution of direct runoff and base flow

Question 18

Why do we separate base flow (hydrograph separation)?

Answer 18

-to quantify the contribution of precipitation and ground water to stream flow
-to identify water quality associated with surface water and subsurface water

Question 19

Hydrograph separation methods?

Answer 19

-straight line
-fixed base
-variable slope