1	Groundwater Supplies Under the influence of surface water
2	Contributors Jim Touw, HCL Norm Zastre, The Groundwater Centre
3	Objective To maintain a groundwater source that is safe to drink Using methods that are practical and at a sensible cost
4	What is groundwater? Recoverable water that occupies voids (porosity) in the subsurface Between grains In fractures In solution cavities
5	GWUDI Ground Water Under the Direct Influence of surface water Subject to the same treatment requirements as surface water If Cryptosporidium or Giardia are present, then GWUDI If Crypto or Giardia are not present, how to determine if GWUDI?
6	Rivers and Lakes
7	Main Source of Groundwater Potable groundwater originates on or near the land surface Therefore, potable groundwater is technically GWUDI The main issue is the pathogenic microbes that can be associated with the surface water
8	A Renewable Resource Most groundwater is recharged from precipitation Usually in late spring/early summer (most years) In summer if there is above-normal precipitation (occasionally) In the fall after vegetation has died and before ground freezes (occasionally)
9	Multi-year Hydrograph
10	GWUDI Areas Not necessarily around rivers and lakes Possible where a downward hydraulic gradient exists
11	How Big is the Problem? Pathogenic microbes Viruses Bacteria Protozoa
12	Pathogens in Groundwater
13	Travel Distance Main factors Porosity type Microbe size Hydraulic gradient Secondary factors Temperature pH Mineralogy
14	Horizontal Distance - Bacteria
15	Frequency – US Groundwater
16	Protoza in US Groundwater
17	Fecal Coliforms - Alberta
18	Alberta Aquifers - Fecal Coliforms
19	Porosity Summary
20	Corral
21	Water Well Pit
22	Is the Groundwater Safe? Water supply well construction – does it meet code? What are the surface conditions within 500 metres of the water supply well? Is treatment necessary?
23	GWUDI Flags Presence of pathogens Turbid groundwater Change in chemical quality Presence of nitrate in the groundwater Elevated concentration of chloride ion
24	Acme Water supply well construction Area of influence Three methods to calculate Field verification Water wells Abandoned/reclaimed Existing Possible contamination sources Agricultural Industrial Municipal
25	Acme Results
26	Conclusions Good news Very little evidence that groundwater is unsafe to drink in Alberta Bad news Very little meaningful data available for analysis
27	Recommendations There is going to be increased interest in the safety of the groundwater in the future Data are being collected by public health, but they are not readily available There is a definite need to bridge the gap between the public health database and the technical database
28	Questions www.hcl.ca/reports.asp