ABCDEF
1
2
Simulating the Risk of Sanitation to Drinking Water from Groundwater
3
4
Introduction:
5
This simple model allows for looking at inter-relationship between various risk factors that contribute to
6
contamination from on-site sanitation.
7
The user can provide estimated values of controlling parameters such as depth to water table, depth of pit, distance to well
8
The output is in the form of the time taken to travel from sanitation to well. Interpretation of this time as risk is provided.
9
10
In this example, parameters have been set to look at a 12 month cycle in which the depth to water table and groundwater gradient are varied.
11
The situation is typical to a monsoonal type rainfall and a hard rock aquifer with very short distance to drinking water well.
12
One can view the individual time taken to reach the water table, to reach the well and the total time taken.
13
14
The user has options of 3 interventions 1. Using drier latrines, 2. Raising the latrine pit and 3. Having the drinking water well farther.
15
The travel time to the well can be seen by making variations on these interventions and see which of them has greater impact.
16
17
Assumptions:
18
19
The model is a simple one in which homogenous aquifer conditions are taken. Also, the unsaturated hydraulic conductivity is estimated
20
by assuming it as a function of hydraulic loading from the sanitation structure. A 100mm/d loading is considered to lead to saturated conditions.
21
From 500 mm/d to 100 mm/d the hysteresis factors is varied from 0.1 to 1 linearly. It is varied from 0 to 0.1 linearly with loading of 0 to 50 mm/d
22
23
Credit:
24
25
The first version has been prepared on June 8, 2011 by Sunderrajan Krishnan from INREM Foundation as inputs into a study support by the
26
Bill and Melinda Gates Foundation look at sanitation-groundwater contamination linkages.
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46