Why you need to use pro­tec­tion

A lit­tle de­tec­tive work re­veals a com­mon is­sue for any­one with bore-supplied drink­ing wa­ter.

NZ Lifestyle Block - - Contents - WORDS ABBY MATTHEWS

In my early days as an en­thu­si­as­tic new groundwater sci­en­tist, I was called to visit a life­style block in the Manawatu. I was met at the gate by a lovely man who was very con­cerned that his wife had be­come sick af­ter drink­ing wa­ter from their pri­vate bore. He had two ques­tions: who was re­spon­si­ble for con­tam­i­nat­ing his wa­ter sup­ply, and what was I go­ing to do about it?

I ar­rived at the farm armed with sam­ple bot­tles, naively think­ing this was go­ing to be my Erin Brock­ovich mo­ment and feel­ing ev­ery bit the ‘CSI’ sci­en­tist.

I sur­veyed the sur­round­ings. The ‘bore’ wasn’t a bore but an open con­crete well. A lit­tle gravel-bed creek next to the prop­erty was un­fenced and the pad­dock around it was full of stock. “Sir, how deep is your... bore?” Peo­ple of­ten as­sume that if wa­ter comes out of the ground it is go­ing to be safe to drink. Un­for­tu­nately, this isn’t al­ways the case. The 2016 out­break of campy­lobac­ter in the Have­lock North wa­ter sup­ply has drawn at­ten­tion to the im­por­tance of en­sur­ing wa­ter sup­plies are safe and se­cure. Dis­cus­sion and de­bate around the po­ten­tial cause of the out­break also high­lighted the range of ways in which bore wa­ter can be­come con­tam­i­nated.

How we treat our land and wa­ter­ways can im­pact the qual­ity of groundwater, and this was cer­tainly the case for the block owner I met that day. How­ever, it is by no means the only way that wa­ter sup­plies can be­come con­tam­i­nated.

Wa­ter on the move

Groundwater forms part of the larger flow­ing wa­ter sys­tem that is con­nected to our rivers, lakes and streams. Wa­ter moves through spa­ces be­tween soil and rock, and is pumped to the sur­face to sup­ply wa­ter for a range of uses.

Un­con­fined aquifers

Most stock wa­ter and do­mes­tic groundwater sup­plies in New Zealand are drawn from shal­low sand and gravel aquifers that have formed in old river chan­nels. Of­ten this groundwater is ‘un­con­fined’, mean­ing that the aquifer has a di­rect path to the land sur­face. Wa­ter in shal­low groundwater sys­tems is of­ten recharged di­rectly from rain­fall or from wa­ter lost from the base of streams and rivers. This means that shal­low groundwater can be quickly re­plen­ished.

How­ever, it also means there is an in­creased risk of con­tam­i­na­tion from nu­tri­ents and bac­te­ria which can be read­ily trans­ported by wa­ter mov­ing through soils and wa­ter­ways into the groundwater sys­tem.

Con­fined aquifers

In deeper aquifers, lay­ers of sed­i­ment such as clay and mud­stone cre­ate a bar­rier (known as a con­fin­ing layer) that re­stricts the flow of groundwater be­tween the aquifer and the sur­round­ing rock. Wa­ter in deep, con­fined aquifers can be hun­dreds or even thou­sands of years old. Be­cause of the time it takes for wa­ter to reach these aquifers, there is gen­er­ally a low risk of con­tam­i­na­tion from bac­te­ria or nu­tri­ents.

Wa­ter qual­ity in con­fined aquifers can be very good, but can also be nat­u­rally min­er­alised and con­tain high lev­els of iron, man­ganese or ar­senic. Soils and ge­ol­ogy play an im­por­tant role in the qual­ity of groundwater and its suit­abil­ity for dif­fer­ent uses.

Newspapers in English

Newspapers from New Zealand

© PressReader. All rights reserved.