GROUNDWATER MONITORING TECHNIQUES

Unlike surface water, wherein information on direction of movement, velocity, sources of contamination are available; monitoring of groundwater involves various investigation prior to the actual assessment of groundwater quality. The topography , soil profile, geology, aquifer characteristics, land-use pattern, source of pollution and above-all, the extent of groundwater development are some of the important pre-requisites to decide the scheme of groundwater monitoring. For a representative information on groundwater quality the first information to look for is the movement of groundwater.

Pic. : 8 : Improper Proper Septic Tank / Flush Waste -
a source of bacterial contamination of groundwater

Table -3 : Common inorganic constituents of Ground water and their impact

Constituents
Impact

Nitrate

  • Carcenogenicity in adults in acute exposure
  • Infantile methelogloboanemia (blue baby syndrome) in acute exposure. It can also be reported in adults

Fluoride

  • Mottling of tooth enamel
  • Crippling of bones

Hardness
(Chloride Sulphates
bi-carbonates)

  • Scaling of (consumer) appliance
  • Less foaming

Sodium

  • Hypertension
  • Congestive cardiac failure
  • Renal disease

Arsenic

  • Hemorrhage in gastro intestinal tract
  • Sloughing of mucosal epithelium
  • Cardio-vascular disease (Reynold’s sydrome)
  • Hyper pigmentation
  • Gangarine

Selenium

  • Acute respiratory distress
  • Irritation and dermatitis
  • Central nervous system disorder
  • Liver necrosis
  • Gastroenteritis

Chromium

  • Respiratory Carcenogenicity
  • Alergic dermatitis

Lead

  • Retarded mental growth
  • Kidney disorder
  • Gonadal dysfunction
  • High Blood Pressure
    •

 


Pic 9 : Waste burial sites contribute
significantly in groundwater pollution

Monitoring of Groundwater Quality

In general, monitoring of groundwater quality involves collection of representative sample and simultaneous collection of hydro-geological information about the sampling location. The sample and hence the groundwater quality data may adversely affect if one or more of the following factors are not appropriately looked into.

a) Sample was taken from stagnant water in the open well or suddenly in case of bore well without removing the casing storage effect. The error can be largely overcome if 3 to 10 well-bore volumes are removed and in case of hand pumps- sufficient water is pumped out before taking the sample.

b) Samples are not taken at appropriate time intervals-seasonally and at improper locations.

c) Contamination due to entrained sediment.

d) Hydraulic characteristics of the (soil) formation near the screen , resulting in possible dilution of the contaminant.

e) Release of carbon-di-oxide during pumping and hence increase in pH which may cause many metallic ions to come out of solution.

f) The samples preservation is not properly done and analyzed without considering the parameter- specific prescribed period of retention.

Tracer Studies

Groundwater monitoring in several cases involves placing a tracer such as, dye or salt in one well and noting the time of its arrival in a second well, down-gradient from the first. Tracers are used to determine groundwater flow patterns, the age of groundwater, geologic and geophysical origin of groundwater, volume of water, physico-chemical characteristics of the aquifer etc. The ability of tracer to indicate dispersion of pollutants is important because dilution rate of any pollutants is extremely important in assessing the severity of pollution problems