Applied Linear Referencing Mapping Salinity in the South Old River

Aaron Cuthbertson, ES, O&MBarry Montoya, Staff ES, O&M

SWRCB has set salinity objectives for the South Delta

South Old River at times exceeds salinity objectives set by SWRCB

The objective of the study is to gain a better understanding of the sources of salinity in the South Old River

Background – Salinity in SOR

Background – Salinity in SORLead Scientist – Barry Montoya

Began doing transects of SOR in 2009

Salinity is typically measured by Electrical Conductivity (EC) – the more conductive a solution is, the saltier. Seawater conducts electricity very well; distilled water conducts very poorly.

Background – Sampling Equip

6 MPH

EC Sensor

GPSDatalogger

Background – Transect route

Background – Lots of DataMany transects recorded

Under different tidal conditions

During different times of the year

Problem – GPS (XY) CoordinatesHow do we compare one transect with

another based on GPS coordinates?

How do we compare transect data to fixed features along the river?

Problem – GPS (XY) Coordinates

USS Enterprise GIS

What do we want?Ability to easily compare different transects

based on location of data points

Ability to compare transects to important features on river, such as discharge pipes

Solution: Simplify the data

Simplify the data

How do we convert XY to dist?

Linear Referencing in ArcGIS

Route feature classroute = polyline feature class with an

embedded measurement system

In ArcGIS, the term route refers to any linear feature, such as a city street, highway, river, or pipe, that has a unique identifier and a common measurement system along each linear feature.

Create a reference line (route)

Create a reference line (route)

Linear Referencing - process

X Y EC

Route Feature Class

Point Feature class

Locate features

along routes

tool

Distance ECEvent Table