IPN-ISRAEL, 17th-19th Sep, 2014

The WaTrend System

Meir Rom, D.Sc.Statistician and System Analyzer

IPN-ISRAEL, 17th-19th Sep, 2014

The WaTrend System

Rapid Characterization and Prediction of Long

Term Water Quality Changes in Ground Water

and Surface Water Resources

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Contributors:

Sharon Hassid, Evgeny Kleiman, Ami Einav

Mekorot, System Information Unit

IPN-ISRAEL, 17th-19th Sep, 2014

Facts and Figures

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3,000 Facilities12,000 km

of water lines

1,070 Water well drillings

IPN-ISRAEL, 17th-19th Sep, 2014

Objectives

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Characterize and Identify large number of

water resources, thru historical records in few

seconds

Predict values of water quality using simple

statistical tools

No need to have special skills in Statistics.

Background calculations.

Interactive, friendly multi-utilities GIS

environment

IPN-ISRAEL, 17th-19th Sep, 2014

Usages (Already Operational)

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Hydrological surveys

Reveal potential contamination and

its source

Prepare for new regulations and

standards

Exploratory Data Analysis (EDA)

tools

IPN-ISRAEL, 17th-19th Sep, 2014

Input

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Mekorot’s water-quality data-base:

spatial and temporal historical data of all

quality parameters.

User must indicate, district, time-window

and choose specific quality parameter.

Mekorot’s water supply data-base

mainly for filter-out “inactive” water

resources

IPN-ISRAEL, 17th-19th Sep, 2014

Why use robust measures?

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Regression (slope)%

Robust (slope)

100%

116%

207%

267%

Leverage Points

Nitrate (NO3) – Ein-Hod

IPN-ISRAEL, 17th-19th Sep, 2014

Trend measure

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Calculate robust measure of trend monotony

Here we used “kendall’s tau”( ): a well known statistical measure.

In map, Adjust the “raduis” of the “star” shape label in proportion to the value of .

Use Green color to indicate decrease of values.

Important: High level of does not necessarily indicate high slope level !

IPN-ISRAEL, 17th-19th Sep, 2014

SD measure

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• Categorize all values into 5 groups, corresponding to the threshold concentration acceptance level.

• Process the relative-frequencies of each category in the specified time-window.

• Transform the results into [0,1] index means that all values in the time-

window exceed the standard level.

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• In map, Adjust the radius of the “diamond” shape label in proportion to .

IPN-ISRAEL, 17th-19th Sep, 2014

Theil-Sen’s robust measure of slope

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Use robust measure (Theil-Sen slope estimator) to

estimate the trend’s rate and test for its statistically

significance.

Determine linearity of trend by halving the time-window

and perform a significant comparison test. In case of non-

linearity report slope results of the window’s second half.

Set icon for each water resource to illustrate its dynamic

behavior in time which corresponds to the specific quality

parameter

IPN-ISRAEL, 17th-19th Sep, 2014

Spatial GIS maps

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IPN-ISRAEL, 17th-19th Sep, 2014

Summary table

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Summary for all characteristics associated with each

water resource is given in dynamic table:

IPN-ISRAEL, 17th-19th Sep, 2014