GES 121 - Winter 2025 Lab 4: Hydrology

These flashcards cover key concepts and definitions related to hydrology as discussed in GES 121 lab.

Hydrograph

A graph of stream discharge over time.

Peak flow

The maximum discharge of a stream during a specific period.

Runoff volume

The total volume of water that flows over the land surface into streams.

Impervious surfaces

Surfaces that do not allow water to penetrate, leading to higher runoff rates.

Pervious surfaces

Surfaces that allow water to infiltrate, promoting soil absorption.

Lag time

The delay between peak rainfall intensity and peak stream discharge.

Urbanization impact on stream discharge

Urbanization decreases lag time and increases peak stream discharge.

Drainage basin

An area of land where precipitation collects and drains off into a common outlet.

Tributaries

Smaller streams or rivers that flow into a larger stream or river.

Strahler’s Stream Order

A method of classifying the hierarchy of streams based on their size and location.

Bifurcation Ratio

The ratio of the number of streams of any order to the number of streams of the next highest order, remaining roughly constant.

Mean Length

Total stream lengths divided by the number of segments.

Cumulative Mean Length

The addition of mean lengths for all streams of a given order.

Scale bar

A reference tool on a map indicating the proportion of distance represented.

River System

A river system consists of a main river, or trunk, which is connected to smaller rivers or streams, known as tributaries, that flow into it. The complete system forms a drainage basin. The pattern of channels is called the drainage network. These networks can have different patterns depending on the landscape.

Strahler’s stream order

When two streams of equal order meet, the result is a stream of greater order. Start with the furthest tips, label them “1” (first order steam).

When two “1” steams meet up, they become “2” (second order stream.

Continue this process until you reach the largest stream.

When two streams of different orders meet, nothing changes.

Stream length

Average length of segments increase with stream order.