176
C. Saliternik
groundwater pollution is in most cases still in a non-steady state and its rate changes with
time makes this process hard to investigate.
Since the subject under study is so highly complex, laboratory tests made in
experimental columns in order to examine the rate of groundwater pollution by nitrogen
compounds were of only limited significance.
Statistical processing of phenomena of groundwater pollution by nitrates as functions
of different parameters can succeed and may be useful, provided that the number of wells
in the sample is large and the relevant background data are available.
In Israel, the possibility of collecting information and relevant background data on
groundwater pollution is exceptionally great, because of the ready availability of detailed
hydrological data on watertables, quantities of pumped water, of geological data on the
profile of most of the operation wells and observation wells; of data on fertilizer
application rates and crop rotations; and of data on the location of sewage treatment
plants, refuse disposal plants, and results of chemical analyses of water from a large
number of wells.
In view of the large potential of available data and the complexity of the process of
groundwater pollution, comprehensive statistical processing by computer was decided on.
The aim of this processing is twofold:
(i) Preparation of a system which would facilitate study and follow-up on the rate of
groundwater pollution, mainly by nitrates, over the years.
(ii) An attempt to locate the central factors affecting the rate of groundwater pollution
by nitrates.
Data Collection
A sample was prepared comprising 900 wells producing 420 MCM/year, or 70 percent
of all pumped groundwater in Israel. The data included in the card index were the
following:
(i) Data on identification and location of each well: co-ordinates, data of drilling,
drainage basin;
(ii) Technical data on each well: depth, length of perforation, quantity of water pumped
annually, intensity of saturated profile to head of perforation;
(iii) Environmental data: topography of the area adjoining the well, type and
composition of soil, type of crops;
(iv) Data on nearby sources of pollutants: refuse, sewage disposal, fertilizer application
rates, livestock enclosures;
(v) Geological data: breakdown of the geological profile, computed permeability;
(vi) Hydrological data: groundwater table, flow gradient (J), transmissivity (T), type of
aquifer, base of aquifer, direction of groundwater flow;
(vii) Chemical data inclusive of all chemical analyses from the data of drilling onward.
Data Processing
For the processing of these data, computer programmes were worked out which made
it possible to classify the data according to different criteria with relation to nitrate
concentrations in wells and according to multi-dimensional regression.
The main findings are given in Figs. 5, 6 and 7.
C. Saliternik
groundwater pollution is in most cases still in a non-steady state and its rate changes with
time makes this process hard to investigate.
Since the subject under study is so highly complex, laboratory tests made in
experimental columns in order to examine the rate of groundwater pollution by nitrogen
compounds were of only limited significance.
Statistical processing of phenomena of groundwater pollution by nitrates as functions
of different parameters can succeed and may be useful, provided that the number of wells
in the sample is large and the relevant background data are available.
In Israel, the possibility of collecting information and relevant background data on
groundwater pollution is exceptionally great, because of the ready availability of detailed
hydrological data on watertables, quantities of pumped water, of geological data on the
profile of most of the operation wells and observation wells; of data on fertilizer
application rates and crop rotations; and of data on the location of sewage treatment
plants, refuse disposal plants, and results of chemical analyses of water from a large
number of wells.
In view of the large potential of available data and the complexity of the process of
groundwater pollution, comprehensive statistical processing by computer was decided on.
The aim of this processing is twofold:
(i) Preparation of a system which would facilitate study and follow-up on the rate of
groundwater pollution, mainly by nitrates, over the years.
(ii) An attempt to locate the central factors affecting the rate of groundwater pollution
by nitrates.
Data Collection
A sample was prepared comprising 900 wells producing 420 MCM/year, or 70 percent
of all pumped groundwater in Israel. The data included in the card index were the
following:
(i) Data on identification and location of each well: co-ordinates, data of drilling,
drainage basin;
(ii) Technical data on each well: depth, length of perforation, quantity of water pumped
annually, intensity of saturated profile to head of perforation;
(iii) Environmental data: topography of the area adjoining the well, type and
composition of soil, type of crops;
(iv) Data on nearby sources of pollutants: refuse, sewage disposal, fertilizer application
rates, livestock enclosures;
(v) Geological data: breakdown of the geological profile, computed permeability;
(vi) Hydrological data: groundwater table, flow gradient (J), transmissivity (T), type of
aquifer, base of aquifer, direction of groundwater flow;
(vii) Chemical data inclusive of all chemical analyses from the data of drilling onward.
Data Processing
For the processing of these data, computer programmes were worked out which made
it possible to classify the data according to different criteria with relation to nitrate
concentrations in wells and according to multi-dimensional regression.
The main findings are given in Figs. 5, 6 and 7.