Hydrologic Measurement

• Precipitation• Evaporation• Streamflow• Channel Properties• Topography• GIS datasets

Reading: Applied Hydrology Chapter 6

Hydrologic Measurement

Precipitation, Climate, Stream Gaging Water Quality Sampling

Precipitation Station

• Tipping Bucket Raingage– The gauge registers

precipitation (rainfall) by counting small increments of rain collected.

– When rain falls into the funnel it runs into a container divided into two equal compartments by a partition

– When a specified amount of rain has drained from the funnel the bucket tilts the opposite way.

– The number and rate of bucket movements are counted and logged electronically.

Tipping bucket rain gage

Weather/climate station

• Following variables are recorded– Wind

velocity/direction– Rainfall– Relative humidity and

temperature– Radiation

Components of a weather station

Anemometer

Radiometer

Tipping bucket raingage

Relative humidity and temperature

Precipitation (continued)

• Snow Pillows

http://wsoweb.ladwp.com/Aqueduct/snow/pillow.htm

8

Snow Pillows

Evaporation pan

Measuring streamflow

Streamflow using a boat

Tag line

Measurement at high flows

Using stream gaging cable car

From bridge

13

Acoustic Doppler Current Profiler

Schematic of a stilling well gaging station

Pressure transducer gaging station

Stream Flow Rate

A

Q AdV

Discharge at a cross-section

Water Surface

Depth Averaged Velocity

Height above bed

%60

%40

Velocity

n

iiii wdVQ

1**

iw

id

1i ni

Velocity profile in stream

Example

distance depth velocity(ft) (ft) (ft/s)

i d V1 0 0 02 12 3.1 0.43 32 4.4 0.94 52 4.6 1.15 72 5.7 1.36 92 4.5 0.77 112 4.4 0.98 132 5.4 1.49 152 6.1 2.0

10 167 5.8 2.211 182 5.7 2.512 197 5.1 3.113 212 6.0 3.114 227 6.5 3.015 242 7.2 2.616 257 7.2 2.017 272 8.2 1.618 287 5.5 2.019 302 3.6 1.620 317 3.2 1.221 325 0.0 0.0

0

1

2

3

4

5

6

7

8

9

0 25 50 75 100 125 150 175 200 225 250 275 300 325

Distance

Dep

th

Colorado River at Austin

Example (Cont.)Distance Depth Velocity Width Area Discharge

(ft) (ft) (ft/s) (ft) (ft2) (ft3/s)i d V w A Q

1 0 0 0 6 4.7 0.02 12 3.1 0.4 16.0 49.6 18.43 32 4.4 0.9 20.0 88.0 76.64 52 4.6 1.1 20.0 92.0 100.35 72 5.7 1.3 20.0 114.0 152.86 92 4.5 0.7 20.0 90.0 63.97 112 4.4 0.9 20.0 88.0 76.68 132 5.4 1.4 20.0 108.0 153.49 152 6.1 2.0 17.5 106.8 216.7

10 167 5.8 2.2 15.0 87.0 193.111 182 5.7 2.5 15.0 85.5 214.612 197 5.1 3.1 15.0 76.5 234.113 212 6.0 3.1 15.0 90.0 280.814 227 6.5 3.0 15.0 97.5 288.615 242 7.2 2.6 15.0 108.0 283.016 257 7.2 2.0 15.0 108.0 220.317 272 8.2 1.6 15.0 123.0 191.918 287 5.5 2.0 15.0 82.5 168.319 302 3.6 1.6 15.0 54.0 84.820 317 3.2 1.2 11.5 36.8 43.421 325 0.0 0.0 4.0 3.2 0.0

325 1693.0 3061.4

0

1

2

3

4

5

6

7

8

9

0 25 50 75 100 125 150 175 200 225 250 275 300 325

Distance

De

pth

Q = 3061 ft3/s

V = Q/A = 1.81 ft/s

19

Rating Curve

• It is not feasible to measure flow daily.• Rating curves are used to estimate flow from stage

data• Rating curve defines stage/streamflow relationship

0

2

4

6

8

10

12

14

16

18

20

0 5000 10000 15000 20000 25000 30000

Discharge (cfs)

Sta

ge

(ft)

Discharge GageHeight

(ft3/s) (ft)20 1.5

131 2.0307 2.5530 3.0808 3.5

1130 4.01498 4.51912 5.02856 6.03961 7.05212 8.06561 9.08000 10.09588 11.0

11300 12.013100 13.015000 14.017010 15.019110 16.021340 17.023920 18.026230 19.028610 20.0

http://nwis.waterdata.usgs.gov/nwis/measurements/?site_no=08158000

Water Watchhttp://waterwatch.usgs.gov/new/

http://www.drought.unl.edu/dm/archive.html

Improvements from Senate Bill 2:Instream Flow requirements

• Requires TPWD, TWDB, TCEQ to develop procedures for defining instream flow requirements

• Implemented on priority study regions by 2010

• Based on fish habitat analysis

Priority Study Regions

Guadalupe

San Antonio

Brazos

Trinity

Sabine

Process Flowchart

Instream Flow

Decision Making

Hydrodynamic

Model

Habitat

Descriptions

Habitat

Model

ArcGISSMS/RMA2 Data Collection and

some statistics

Depth & velocity

Species groups

Criterion

Study Area (Guadalupe river near Seguin, TX)

1/2 meter Digital Ortho Photography

Depth Sounder (Echo Sounder)

The electronic depth sounder operates in a similar way to radar It sends out an electronic pulse which echoes back from the bed. The echo is timed electronically and transposed into a reading of the depth of water.

Acoustic Doppler Current Profiler

Provides full profiles of water current speed and direction in the ocean, rivers, and lakes. Also used for discharge, scour and river bed topography.

Measurement System

GPS Antenna

Depth Sounder

Computer and power setup

Channel Bed Soundings

Bathymetry from Side-Scanning Sonar

Channel demo

National Elevation Dataset

• Digital Elevation Model with 1 arc-second (30m) cells

• Seamless in 1° blocks for the United States

• 10 billion data• Derived from USGS 1:24,000 quadrangle

sheets

http://seamless.usgs.gov/Get the data:

http://ned.usgs.gov/

Digital Elevation Model (DEM)

Contours

720

700

680

740

680700720740

720 720

Austin West 30 Meter DEM

32

16

8

64

4

128

1

2

Eight Direction Pour Point Model

Water flows in the direction of steepest descent

Flow Direction Grid

32

16

8

64

4

128

1

2

Delineation of Streams and Watersheds on a DEM

Watersheds of the US

2-digit water resource regions 8-digit HUC watersheds

Hydrologic Unit Code Watersheds

~ 2000 for US, about the size of counties

38

LIDAR surveying

LIDAR (Light Detection and Ranging; or Laser Imaging Detection and Ranging) is a technology that determines distance to an object or surface using laser pulses. Like the similar radar technology, which uses radio waves instead of light, the range to an object is determined by measuring the time delay between transmission of a pulse and detection of the reflected signal.

3-D detail of the Tongue river at the WY/Mont border from LIDAR.

Roberto GutierrezUniversity of Texas at Austin

http://srtm.usgs.gov/

HydroSheds derived from SRTM

http://hydrosheds.cr.usgs.gov/

River networksfor 8-digit HUC watersheds

http://nhd.usgs.gov/

Lower West Fork, Trinity River BasinHUC = 12030102

http://www.horizon-systems.com/nhdplus/

NHDPlus for a Portion of Oregon

http://www.horizon-systems.com/nhdplus/

NHDPlus Reach Catchments ~ 3km2

About 1000 reach catchments in each 8-digit HUC

Average reach length = 2km 2.3 million reaches for continental US

http://www.ncgc.nrcs.usda.gov/products/datasets/statsgo/

1:250,000 Scale Soil Information

Ssurgo for Travis County

103 soil map units described by 7530 polygons of average area 35.37 ha (87 acres)

National Land Cover Dataset

http://seamless.usgs.gov/Get the data: