Chng 1

B mn: K thut mi trng Lp: H CN Ha 1_K3

Li ni u

Nc ngun ti nguyn v cng qu gi nhng khng phi v tn. Mc d lng nc chim hn 97% b mt tri t nhng lng nc c th dng cho sinh hot v sn xut rt t, ch chim khong 3%. Trong nc ngm l mt thnh phn khng th thiu v ng mt vai tr rt quan trng b sung ngun nc cho nhn loi, vic khai thc v s dng nc ngm l mt yu cu tt yu v ngy cng ln. Nhng hin nay ngun nc ny ang b nhim trm trng do nhiu nguyn nhn m nguyn nhn chnh l do hot ng sn xut v thc ca con ngi.

ti ny tm hiu r v nc ngm, tnh trng nhim nc ngm v cc bin php x l nhm nng cao cht lng nc ngm trong sinh hot v sn xut.Thc hin

1. inh Th H

2. Nguyn Tt Thnh

3. H Th ThoaCHNG 1KHI QUT V NC NGM1.1. Vai tr ca nc ngm trong i sng v pht trin kinh t

Nc lun lun gi mt vai tr mang tnh sng cn trong lch s pht trin loi ngi v pht trin kinh t x hi ca mi quc gia. Trong thi i hin nay do bng n v dn s, do cc ngnh kinh t ca cc nc trn th gii thi nhau pht trin nh v bo, cht lng cuc sng ca con ngi ngy mt nng cao v th yu cu v nc ngy mt ln, cc ngun nc c khai thc v s dng ngy cng nhiu. Nhn chung trn tri t c 3 ngun nc chnh: Nc ma, nc mt, nc ngm. mi ni trn tri t lng nc ma cung cp hng nm u c hn, mt khc ma li phn phi khng u theo c khng gian ln thi gian. Nhng vng ma nhiu lng ma nm bnh qun cng ch t 2000 2500 mm, nhng vng ma t ch t 400 500mm, c nhng vng khng h c ma. nhng ni c ma, lng ma cng phn phi khng u trong nm, nhiu thi gian ko di khng c ma. nhng vng c cc nc cng nghip pht trin, thm ch nc ma cng b nhim mt cch nng n, i khi xut hin nhng trn ma acid hoc ma bn Chnh v vy, ngun nc ma t lu khng th p ng y yu cu v nc ca con ngi.

Ngun nc mt trn tri t cng c khai thc v s dng mt cch qu mc nn ngy cng b hao ht v khi lng, suy gim v cht lng, c nhiu ni trn th gii ngun nc mt khng c hoc rt khan him khng s dng, nhiu ni lng ma hng nm nh hn lng bc hi nn nc mt hu nh khng c nh cc vng sa mc hoc cc nc Trung Phi, Nam

Vi nhng l do trn, ngun nc ngm trc mt cng nh lu di ng mt vai tr rt quan trng b sung ngun nc cho nhn loi, vic khai thc v s dng nc ngm l mt yu cu tt yu v ngy cng ln.

mt s nc trn th gii t lu yu cu khai thc s dng nc ngm rt ln c bit s dng nc ngm vo mc ch sinh hot v chn nui.

Trn ton th gii nc ngm c khai thc p ng 50% yu cu nc cho sinh hot ca nhn loi.

Ngoi mc ch khai thc nc ngm cho sinh hot, nc ngm cn c khai thc phc v cho nng nghip, trng trt, chn nui v cc ngnh kinh t khc.

Nng nghip: nhiu nc trn th gii s dng nc ngm ti cho cc din tch trng trt: Din tch canh tc c ti bng nc ngm ca mt s nc nh sau:

- Brazin c 22.000 ha- Angieri c 80.000 ha

- Hy Lp c 30.000 ha

- Nga, Trung Quc, M c 15% lng nc ti l nc ngm.

Nc ngm cng c khai thc p ng cho yu cu cho cng nghip v chn nui hu ht cc nc trn th gii. Cc nc ln nh: Nga, M, Trung Quc, n , Autralia, Ai Cp, Nam Phi u khai thc v s dng nc ngm vi qui m rt ln v cn ang tip tc c m rng trong tng lai p ng yu cu ngy mt cao ca kinh t dn sinh.

Vit Nam, tuy l mt nc nhit i ma nhiu, ngun nc mt tng i phong ph nhng yu cu khai thc nc ngm cng rt ln. T u th k 20, chng ta bt u khai thc nc ngm phc v cho sinh hot v cng nghip cc thnh ph ln nh: H Ni, Hi Phng, Nam nh, Vinh, Hu, TP H Ch Minh nng thn, cc h gia n t lu s dng ging khoan, ging o khai thc nc ngm dng cho sinh hot.

Nhng nm gn y, nc ta tc pht trin kinh t v th ha rt cao, hng lot cc thnh ph ln, th x, th trn mi c mc ln, hng lot khu dn c, khu ch xut hnh thnh v i vo hot ng, cc vng kinh t mi min ni pha Bc, cao nguyn v ven bin c thit lp. Din tch trng trt trong nng nghip tng nhanh, cy trng c a dng ha. Yu cu v cp nc ni chung rt ln, yu cu khai thc s dng nc ngm c bit nhng khu vc khan him nc mt li cng ln v cp thit.c im ca nc ngm:

u im:

- Nc ngm phn b khp ni, ngun nc tng i n nh.

- Nc ngm thng c khai thc v s dng tai ch, ng dn nc ngn tn tht nc trong qu trnh dn nc t.

- Lu lng khai thc nc ngm nh nn qui m xy dng cng trnh khng ln, ph hp vi ngun vn a phng v ca cc h dn cn khai thc v s dng nc ngm.

- Cht lng nc ngm tt hn nc mt nn x l t phc tp.

- nhng vng trng v ly tht, khai thc nc ngm d dng, t tn km ngoi ra cn c th h thp mc nc ngm ci to t.

Nhc im:

- Lu lng nh, kh nng cp nc nh nn cng trnh nm phn tn.

- Nc ngm c khong ha cao, nhit nc ngm thng khng ph hp vi yu cu dng nc nn phi x l nc trc khi s dng.

- i hi nng lng bm ht khai thc nc ngm.

- Nu nc ngm nm qu su cng trnh khai thc s phc tp dn n gi thnh khai thc nc s cao.

- Vic khai thc nc ngm khng hp l s n nhim mi trng, lm mt cn bng sinh thi t nhin. cc vng duyn hi nu khai thc nc ngm qu mc, mc nc ngm h thp, nc mn t bin s xm nhp lm nhim ngun nc ngm.

Tm li: Vai tr ca nc ngm ngy cng quan trng trong pht trin Kinh t - X hi ca mi Quc gia. V vy khai thc nc ngm l vn c nh hng rt ln n nn kinh t ca mi Quc gia. Nhng c ngm khai thc qu mc, khoan ging trn lan, th ngun nc ngm s ngy cng nhim.1.2. S hnh thnh nc ngmC nhiu gi thuyt v s hnh thnh nc ngm t xa xa. Gi thuyt u tin cho l: Nc ma thm lu xung cc tng t to thnh nhng khu vc cha nc trong lng t. Gi thuyt ny c a ra vo th k trc cng nguyn. Sau gi thuyt ban u dng nh b lng qun cho n tn th k th XVII gi thuyt ny li c nhc ti nh mt gi thuyt hp l nht hi by gi. Mi n 1877 nh a cht hc ngi c tn l O.Phn Gher bc b lun trn v a ra gi thuyt mi l do s ngng t nc trong t. ng khng nh rng s hnh thnh nc ngm trong t c bn khng ch l do thm lu nc ma m cn do qu trnh xuyn su khng kh v hi nc vo k rng lp v Tri t v hi nc b ngng t khi hp thu lnh ta thnh nhng vng cha nc ngm trong lng t. S bn ci v gi thuyt ny din ra rt si ni, nhiu kin phn i lun im trn v khng cng nhn v n cha l gii c chn vn v ton din cc vn , ng nhin lun im ban u li c bo v, mc du bn thn n cha gii thch r ngun gc pht sinh nc ngm. Mi sau ny, vo th k XX nh bc hc ngi nga A.F.Rebegeb trn c s nghin cu th nghim chng minh v gii thch qu trnh hnh thnh nc ngm khc vi Phn Gher ch tnh xuyn su ca khng kh c ng gii thch l do qu trnh chnh lch n hi hi nc tn ti trong cc tng t to ra. Hi nc chuyn v t vng c n hi cao ( nhit cao) xung vng c n hi thp ( nhit thp). ng nhn mnh ch do hin tng ngng t hi nc cha gii thch mi hin tng trong qu trnh hnh thnh nc ngm m phi kt hp cht ch vi lun im ban u. V vy, nc ngm c ngun gc cung cp mt phn l do nc ma ngm xung t, mt khc do ngng t hi nc t su trong long t ha quyn vi nhau m hnh thnh nc ngm. Ni khc i ngun cung cp cho nc ngm ch yu do nc ma v hi nc m ng thi ca chng thng qua s tun hon nc trong t nhin: Nc trn mt t, mt bin, sng ngi, h ao, knh mng bc hi nc ln bu kh quyn. y chng t li thnh nhng lp my dy c v ngng t li ri xung mt t di dng ma. Mt b phn nc ma chy ra sng bin, b phn khc bc hi ln bu kh quyn, mt b phn thm lu su vo t di dng dng thm v hi nc xuyn su b sung cho nc ngm.

Nh vy, ngoi nc ma ra nhn t hnh thnh nc ngm phi k n hi nc chuyn v v pha c s n hi thp c ngha l ni c nhit thp. Nh chng ta bit ma h di mt t lnh hn trn mt t v khng kh em theo hi nc bo ha thm su vo lp v Tri t.

Ti y hi nc c trong khng kh di t b ngng t thnh nc ri cung cp vo tng tr nc. Bi vy, ta c th i ti kt lun: S hnh thnh nc ngm ch yu l do nc ma ngm xung t v hi nc trong khng kh thm vo trong t v c ngng t trong lng t. Vng hnh thnh nc ngm c th l vng di chuyn chm ca nc trong cc k rng ca t, trong cc vt rn nt ca nham thch hoc trong cc hang, ng c to ra trong cc tng nham thch rn chc, to thnh dng chy ngm trong lng t.1.3. Ch nc ngm v phn b nc ngm theo chiu su

1.3.1. Ch nc ngm

Nc ngm l mt thnh phn trong chu trnh tun hon ca nc trong t nhin: Nc trong kh quyn tn ti di dng hi nc hay git ma, ma ri xung t mt phn to thnh dng chy mt mt phn bc hi tr li bu kh quyn cn li s thm vo trong ln t b sung cho nc ngm. Bn canh hi nc t trong kh quyn cng c thm su vo lng t do hin tng chnh lch v nhit v p lc n hi cng vi lng nc t sng, bin, h, ao ngm xung cung cp cho ngun nc ngm. Trong ma kh hn t ma, nc ngm mt phn cung cp cho tng t v s c bc hi ln bu kh quyn thng qua hin tng bc hi mt nc. S tun hon ca nc trong t nhin l mt chu trnh khp kn.

Phn loi cc tng a cht thy vnDa vo tnh cha nc v tnh thot nc ca cc tng a cht c th chia thnh 4 loi tng a cht thy vn:

1. Tng ngm nc v vn chuyn nc.Tng ngm nc v vn chuyn nc l mt h t c kh nng tr nc tt cho php nc vn chuyn c trong h t , nh cc tng ct, ct si.2. Tng ngm nc it v vn chuyn nc km.Tng ngm nc t v vn chuyn nc km l mt h t c kh nng cha nc nhng vn chuyn nc km nh t st pha ct, t st pha cui si.

3. Tng ngm nc nhng khng vn chuyn nc.Tng ngm nc nhng khng vn chuyn nc l mt h t c l rng ln, cc l rng khng thng nhau v khng cho nc vn chuyn qua cc ti nc trong cc hang , cc khe nt ca nham thch c cha nc hoc cc b phn tr nc c bao bc bi tng t st.

4. Tng khng ngm nc v khng vn chuyn nc.

L cc tng a cht rn chc khng cha nc nh cc tng gc lin khi.Nu da theo s sp xp tng i gia cc tng a cht khng thm v cc tng tr nc ng thi da vo cao ca ng p lc nc ngm so vi tng khng thm nc c th chia tng tr nc lm 2 loi:- Tng tr nc c p- Tng tr nc khng p- Tng tr nc c p bin thnh tng tr nc khng p khi ng p lc h thp hn tng khng thm pha trn ca tng tr nc.- Nc ngm treo (ti nc ngm) l loi nc ngm tn ti dng cc ti nc nm trong cc tng a cht c bao bc bi cc tng a cht khng thm nc.

Trn quan im nc di t ngi ta cn phn cc tng a cht thy vn theo lng nc cha trong t:1. Tng r cyTng r cy l tng hot ng tp trung ca b r ht nc cung cp cho cy trng. Ngun nc cung cp ch yu do ma ngm xung v li dng c mt phn nc ngm cung cp do nc ngm nm cao nc ngm do mao qun leo ln. Tuy nhin tng ny do tip xc vi mt t lng bc thot nc tng i ln. Trong lng bc hi ph thuc ch yu vo cc nhn t kh hu v v tr mc nc ngm.2. Tng trung gian

Tng trung gian l tng ni tip gia tng r cy v tng nc mao qun. Khi nc ngm nm nng th tng ny c kh nng cp nc cho tng r cy v c lng bc thot hi ng k. Nu nc ngm nm su th tng ny c kh nng cp nc khng ng k. V vy lng bc thot nc gn nh bng 0, lng nc tn ti trong tng ny rt nh di dng hi nc ngng t.

3. Tng mao dn

Tng mao dn l tng chuyn ha nc ngm thnh nc mao qun treo v mao qun leo cp nc cho tng trung gian v tng r cy. y l tng c ngha quan trng v s cn bng sinh thi gia t, nc v cy trng.

4. Tng bo ha ncTng bo ha l tng t, c nc cha y trong cc khe k rng ca t . Chiu su ca tng bo ha nc ph thuc vo lng nc cha trong tng tr nc, ngoi ra cn ph thuc vo ngun nc cung cp cho nc ngm nh mc nc sng, h, dng chy ngm, ni cch khc ph thuc cc c tnh ca cc ngun nc khc cung cp cho nc ngm. Vng t bo ha nc thng chu tc dng ca p lc ct nc cha trong t.

5. Tng khng thm nc

Tng khng thm nc l tng a tng khng cho nc ngm di chuyn qua. Ty vo v tr tng i ca tng khng thm vi ng p lc v s lng, dy ca tng khng thm m trng thi nc ngm c th l khng p hoc c p. Thng thng, tng khng thm n lp nm pha di tng tr nc s xut hin nc ngm khng p. Tng khng thm a lp s xut hin nc ngm c p.

CHNG 2

PHN LOI V S BIN NG CA NC NGM

2.1. Phn loi nc ngm

Tiu chun phn loi nc ngm c th quy t v hai loi hnh c bn:- Phn loi nc ngm theo thnh phn ha hc v l hc

- Phn loi nc ngm theo s phn b ca nc ngm trong cc tng a cht

2.1.1. Phn loi nc ngm theo thnh phn ha hc

C nhiu phng php phn loi nc ngm theo thnh phn ha hc ca cc cht cha trong nc ngm, di y l phng php phn loi nc ngm theo thnh phn ha hc ca C.A.Sukarev. Phng php phn loi nc ngm ny c d lun rng ri tha nhn l phng php c c s khoa hc v c nhiu thun li khi s dng thc t.

Nhiu tc gi c cng quan im l da vo s khc nhau ca t s gia cc anion v cation ch yu cha trong nc ngm phn loi.

Theo quan im C.A.Sukarev phn loi nc ngm chng ta da vo hm lng ca 6 anion v cation ch yu cha trong nc ngm sau y:

Nhm anion: Cl-, SO42-, HCO3-Nhm cation: Na+, Mg2+, Ca2+Theo t l gia cc thnh phn trn c th phn chia nc ngm thnh 49 loi, rt thun tin cho vic so snh tnh cht ca tng loi nc ngm tthnh phn ha hc.

Cng trn quan im chung , O.A.Alekin phn chia nc thin nhin thnh:

Ba loi nc theo anion: Nc Cacbonat, nc Sunphat, nc Clo

Ba loi nc theo cation: Nc Canxi, nc Magie, nc Natri

Trong mi mt loi li c chia ra 3 cch phn loi theo t l gia cc ion cha trong nc ngm.

Ngoi ra, cng trn quan im ha hc ngi ta cn da vo hm lng cc cht khong trong nc ngm phn loi:

- Nc nh

- Nc trung bnh

- Nc nng

2.1.2. Phn loi nc ngm theo tnh cht l hc

Cch phn loi ny ch yu da vo ch tiu nhit ca nc ngm phn loi v chia thnh 3 loi nc ngm ch yu sau:- Nc ngm lnh c nhit : t < 200C

- Nc ngm m c nhit : t 20 370C

- Nc ngm nng c nhit : t > 370C

Ngoi ra cn da vo iu kin p lc ca nc ngm phn loi:

- Nc ngm khng p l loi nc ngm c p sut ti cc im trn mt nc ngm bng p sut kh tri.- Nc ngm c p l loi nc ngm c p sut ti tt c cc im trong tng tr nc u cao hn p sut kh tri. Cng c th ni theo mt cch khc ng p lc ca nc ngm nm cao hn tng khng thm p nm pha trn ca tng tr nc.

- Nu nc ngm c p lc cao c kh nng phun nc ln cao khi mt t c gi l nc ngm Artesian.2.1.3. Phn loi theo s phn b ca nc ngm trong cc tng a cht

Trn quan im ny, cc nh nghin cu xut nhiu cch phn loi khc nhau, nhng u c mt im chung l ly cu to v iu kin sp xp a tng lm c s chnh, sau kt hp vi mt s yu t khc nh c tnh thy lc nhn bit cc loi nc ngm. Tuy nhin y l vn v cng phc tp, cho n nay, cha c phng php phn loi no theo quan im ny c tha nhn l u vit nht. Mc d vy, vi cch chia ny nc ngm cng c nhn bit vi nhng c tnh ring ca tng loi.

V d:

- Nc ngm trong cc l hng ca t

- Nc ngm trong cc khe nt ca t

- Nc ngm trong cc hang ng

- Nc ngm tng nng

- Nc ngm tng su

c th hnh dung s phn loi nc ngm theo s phn b ca nc ngm trong cc tng a cht v iu kin sp xp a tng, ta tm phn loi lm 4 loi chnh:

1. Nc ngm tng nng

2. Nc ngm tng su

3. Nc ngm khe nt

4. Nc ngm hang ng

1. Nc ngm tng nngNc ngm tng nng nm trn tng khng thm th nht (khng c tng khng thm ph kn bn trn). y l loi nc ngm khng p. Mt nc ngm l mt nc t do, p lc ti mc nc ngm chnh bng p lc kh tri (P = Pa). Nc ngm tng nng phn b rng khp hu ht mt ni, tr mt s vng c bit. Nc ngm tng nng thng thay i v tr lng cng nh mc nc theo tng thi k trong nm, v n chu nh hng trc tip ca iu kin kh hu, thy vn nh lng ma, nhit , m, tc bc hi mt t mc nc ca cc sng ngi, h ao, m trong khu vc. Ngun cung cp ch yu l do nc ma ngm vo t. Mt khc nc ma cng tp trung vo sng ngi, h, ao, v lng nc mt t sng, ngi, ao, h li theo dng thm b sung trc tip cho nc ngm tng nng.

Ma ma mc nc ngm tng nng c dng cao do c b sung nc t ngun nc ma v ngun nc mt cc ao h sng sui. c bit i vi sng vng ng bng do ph sa bi p, long sng ngy mt cao, mc nc sng thng xuyn cao hn mc nc ngm hai bn b. V vy, sng thng xuyn cung cp nc cho nc ngm tng nng. cc vng trng la nc mc nc ngm tng nng cng c dng cao do nc ngm c b sung nc t cc rung trng la.

Ngc li, v ma kh do b bc hi mt t, mt khc mc nc ao, h hoc cc sng sui h thp, mt s trng hp h thp hn c mc nc ngm tng nng, nc ngm li theo dng thm b sung cho dng chy c bn ca cc sng sui. V vy, mc nc ngm v tr lng nc ngm tng nng u gim.

Tr lng nc ngm tng nng ph thuc vo b dy ca tng tr nc, thnh phn cp phi ht ca tng tr nc.

2. Nc ngm tng su

Nc ngm tng su nm pha di tng khng thm th nht, tng tr nc thng nm kp gia hai tng khng thm. Nc ngm tng su c th nm di mt t t vi chc mt ti hng trm hng nghin mt.Do nm pha di tng khng thm ngn cch nn nc ngm tng su khng c cung cp trc tip ca nc ma hoc nc mt trong vng. Tuy nhin nc ma v nc t dng chy mt vn gin tip lin quan ti tng nc ny thng qua cc dng chy ngm t ni khc ti. Nc ngm tng su c th c p hoc khng c p.

- Nu ngun nc cung cp cho nc ngm tng su khu vc c xut pht t ni c cao trnh cao v c p lc ct nc ln th nc ngm tng su thng c p.

- Ngc li, nu nc khng cha y tng ch nc, v mc nc ngm trong tng tr nc thp hn tng khng thm pha trn th ta c nc ngm tng su khng p.

3. Nc ngm trong khe ntNc ngm khe nt l nc cha trong cc khe nt ca nham thch, nhng khe nt ny c to ra do qu trnh kin to a cht hoc do ng t, ni la lm cho cc tng nham thch b t gy hoc nt n. Nc ngm trong khe nt c th c hnh thnh cng vi s hnh thnh ca cc khe nt hoc c cung cp t ngun nc ma, ngun nc cc ao, h, sng, sui thng qua dng thm vo cc khe nt.

4. Nc ngm trong hang ngCc hang ng xut hin do s xm thc ca nc vo nham thch to thnh cc hang ng. Nc t cc ngun nc mt, nc mch hoc nc ngm t cc ni khc tp trung v cc hang ng thnh cc dng chy ngm hoc cc h cha nc ngm trong cc hang ng nm su trong lng t. Nc trong hang ng thng xut hin vng ni vi, bch vn, thch cao, mui m Tr lng nc ngm trong hang ng ty thuc vo kh nng tp trung nc, kch thc ca cc hang ng v ph thuc vo cc ngun cung cp vo cc hang ng, s lu thng gia ngun nc v cc hang ng. Nc ngm hang ng c th c dng c p hoc khng p, thng thng nc ngm hang ng c khong kh cao.

2.2. S thay i nc ngm v cc yu t nh hng

2.2.1. S thay i nc ngm

- Nu xt trong thi gian di, qu trnh thay i nc ngm cng tng t nh nc mt. Trong ma kh lng ma t, mc nc cc ao h thp, dng chy cc sng sui nh, lng bc hi ln v th mc nc ngm thng h xung thp, ngc li trong ma ma. Ma nhiu, nc mt nhiu mc nc ngm s dng cao tr lng nc ngm s phong ph. Tuy nhin, s thay i ca nc ngm cn ph thuc vo rt nhiu yu t khc nh tnh thm ca t kh nng tr nc ca tng tr nc.- Trong chu k mt nm, ma kh mc nc ca nc mt h thp, nhiu trng hp thp hn mc nc ngm, nc ngm thng qua cc mch nc cung cp nc cho nc mt. Ma ma mc nc ngm thng thp hon mc nc mt, nc mt v nc ma li ngm xung t b sung cho nc ngm. Tng quan gia nc mt v nc ngm thay i theo ma, c thi k nc mt cung cp cho nc ngm v ngc li c thi k nc ngm cung cp cho nc mt.2.2.2. Cc yu t nh hng n nc ngm

Tuy nm su di t nhng tr lng cng nh cht lng nc ngm chu nh hng ca rt nhiu yu t bao gm: Yu t kh hu thy vn trn mt t, cc yu t v a hnh, a mo, th nhng, a cht, cc hot ng pht trin ca con ngi.

1. Yu t khi huLng ma l ngun cung cp ch yu cho nc ngm v th lng ma hng nm, phn phi lng ma trong nm s c nh hng gn nh trc tip n tr lng nc ngm c bit l nc ngm tng nng. Bn cnh cng ma c nh hng trc tip n h s dng chy c ngha nh hng ti lng nc thm xung t cung cp cho nc ngm.

Lng bc thot hi nc: B thot hi nc t mt t l mt thnh phn trong lng nc i ca nc ngm, lm gim lng nc ngm. Cc yu t kh hu nh nhit , m, gi c nh hng trc tip n lng nc bc hi mt t. V th, cc yu t kh hu ny c nh hng trc tip n s thay i ca nc ngm.

2. Yu t thy vnDng chy mt trn cc sng sui, lng nc v mc nc trong cc ao h, tng quan gia mc nc ao h v mc nc ngm c nh hng trc tip n nc ngm; cht lng ca nc mt cng nh hng n cht lng nc ngm. Ngoi ra ch thy triu, tnh hnh hn hn l lt cng c nh hng ti nc ngm.3. iu kin a hnh, a mo, thm ph trn mt t dc a hnh, g gh ca mt t, mt sng sui ao h trn mt t c nh hng n h s dng chy c ngha nh hng trc tip n lng nc thm vo t b sung cho nc ngm.

4. Yu t v a cht, th nhngCch sp xp a tng, cu to ca cc tng a cht, rng ca cc

lp t , h s thm s nh hng ti tc v lng nc thm vo trong t.

5. Cc hot ng pht trin ca con ngi l s khai thc nc ngm phc v cc mc ch pht trin khc nhau, nhng tc ng ca con ngi vo cht lng v khi lng nc mt l ngun nc b sung chnh cho nc ngm. Mt khc cc cng trnh gi nc nh h cha nc, h thng cp thot nc u c nh hng n s thay i ca nc ngm.

Qu trnh th ha thng gy ra nhng s thay i mc nc ngm do kt qu ca vic lm gim lng b sung nc ngm v tng cng vic khai thc nc ngm. nhng vng nng thn nc dng thng c ly t nhng ging nng, trong khi hu ht cc nc thi ca th li tr li t thng qua cc h cha nc bn. Do vy, s nhim bn ca nc ging tng ln. Nhiu ging cc h dng ring phi b i.Ba iu kin lm cho nc ngm gim l:

- Lm gim lng b sung nc ngm do lt b mt

- Bm ht tng

- Gim lng b sung nc ngm do h thng cng ngm thu nhn nc ngm t trn xung.

Ngoi ra cn c nhng nh hng khc ca ng t, nh hng ca ti trng bn ngoi

6. p sut kh quynS thay i p sut kh quyn gy ra do s dao ng mc nc thy p trong tng cha nc c p. Mi quan h l quan h nghch bin, c ngha l tng p sut kh quyn s lm gim mc thy p v ngc li.

7. nh hng ca thy triuTrong nhng tng t cha nc tip gip vi bin, s dao ng ca thy triu dn n s bin ng ca nc ngm.

2.3. Nc ngm Vit Nam v kh nng khai thc, s dng

Cc kt qu iu tra a cht thy vn khu vc v tm kim thm d nu trn cho php phn chia ton lnh th cc phn v a cht thy vn nh sau:- Cc tng cha nc l hng trong cc thnh to t

- Cc tng cha nc khe nt trong cc thnh to bazan. Pliocen t

- Cc tng cha nc khe nt trong cc thnh to lc nguyn

- Cc tng cha nc khe nt Karst trong cc thnh to Cacbonat

- Cc thnh to a cht rt ngho nc hoc khng cha nc

2.3.1. Cc tng cha nc l hngPhn b rng ri ng bng Bc B, ng bng Nam B v cc ng bng ven bin Min Trung.

1. ng bng Bc B

C 2 tng cha nc ch yu l tng cha nc Holocen (qh) v tng cha nc Pleistocen (qp). Tng tr lng (khai thc tim nng ca ND khong 7,5 triu m3/ng).

Tng qh: Phn b hu khp ng bng, thng gp chiu su 20 40m. t cha nc ch yu l ct, sn. giu nc bin i mnh, lu lng l khoan 0,5 10l/s. Vng ven bin nc b nhim mn. Nc trong tng c quan h trc tip vi nc mt. Tng cha nc ny c th p ng yu cu cung cp nc quy m trung bnh u nh. Phn ln cc l khoan ca chng trnh nc nng thn v ca nhn dn khai thc nc trong tng ny.

Tng qp: Nm di tng qh v ngn cch vi tng ny bi mt lp st mu loang l dy 5 20m, thng gp su 50 60m. t cha nc l ct cui si ht th. y l tng cha nc c p, giu nc v c th p ng yu cu khai thc ln. Lu lng l khoan thng ln hn 10 l/s hu ht cc nh my nc ng bng Bc B ang khai thc nc t tng ny. Nc c quan h vi tng qh v nc mt qua cc ca s CTV. Vng ven bin v hai ra ng bng b nhim mn.

2. ng bng Nam BC 5 tng cha nc l hng k t trn xung l cc tng Holocen (qh), Pleistocen trung thng (qp2-3); Pleistocen h (qp1); Pliocen (m4); Miocen (m3). Tr lng khai thc tim nng t khong 27,5 triu m3/ng.

Tng qh: C din tch phn b khong 43.000km2, b dy 20 70m. t cha nc l ct ht nh, ct bt. Nhn chung, tng ny ngho nc, cht lng nc xu thng b nhim mn, nhim phn.

Tng qp2-3: Phn b trn hu ht ng bng din tch khong 50.000km2 . Tng ny nm su 40 80m, b dy 25 135m, trung bnh 5070m t cha nc l ct si. y l tng cha nc phong ph, min ng Nam B cht lng nc tt, vng Ty Nam B nhiu vng b nhim mn.

Tng qp1: c phn cch bi tng qp2-3 bi mt lp st dy 20 25m, i ch ti 50m. Din phn b khong 49.000 km2 . Chiu su th nm 150 200m. B dy tng 50 60m, i khi ti 130m. t cha nc l ct, i khi ln sn si. y l mt tng cha nc phong ph. Cht lng nc bin i nhiu theo din. min ng Nam B chng c quan h vi nc mt v c cht lng tt. min Ty Nam B c nhiu vng b nhim mn.

Tng m4 : C din tch phn b khong 49.000km2, chiu su th nm 150 350m, b dy 50 140m, thng gp 90 100m. t cha nc l ct nhiu c ht ln sn si. y l mt tng cha nc rt phong ph, cht lng nc trong tng bin i theo din. Vng trung tm v ven bin b nhim mn.

Tng m3 : Ngn cch vi Tng m4 bi mt lp st dy 20 50m. Din phn b khong 37.000km2, chiu su mi 200 450m, thng gp 350 400m, b dy 40 100m. t cha nc phong ph, nc c cht lng tt. Vng trung tm v ven bin b nhim mn.

3. Cc ng bng ven bin Min TrungCc tng cha nc c din phn b hp, ko di v khng lin tc, thng gp c hai tng cha nc qh v qp nhng chiu dy nh. Tng cha nc qh gm ch yu l ct, tng qp ch yu l ct cui si. Hin tng nhim mn gp ph bin, nht l trong tng qp.

2.3.2. Cc tng cha nc khe nt trong cc thnh to Bazan Pliocen tPhn b rng vng Ty Nguyn v ng Nam B. Ngoi ra cn gp mt s vng vi din tch khng ln Qu Hp, in Bin t ch yu l Bazan, Olivin, Bazan kim. phong ph nc thay i ln theo din v ph thuc v nt n, b dy v din phn b ca khi Bazan. C ni khi Bazan dy ti 200 300m nh vng Pleiku. Nc trong thnh to Bazan c cht lng tt ph bin l dng nc Bicacbonat Clorua c tng khong ha 0,2 0,3 g/l. Ngun cung cp ch yu l nc ma. ng thi bin i mnh theo ma.

2.3.3. Cc tng cha nc khe nt trong cc thnh to lc nguyn Mesozoi (ms)

Phn b rng ri cc vng ng Bc B, bc Trung B. Ngoi ra cn gp vng Ty Nguyn v Nam Trung B. Chng gm cc trm tch lc nguyn h Tra, Jura, Creta, Neogen. t cha nc ch yu l ct kt, cui kt, sn kt, bt kt, st kt nt n.

Nhn chung, cc tng cha nc ny ngho nc. Tuy nhin, mt s ni c th gp mt s tng ct kt, cui kt nt n kh giu nc, cht lng nc tt, tng khong ha thng 0,01 0,2g/l.

2.3.4. Cc tng cha nc khe nt Karst trong cc thnh to CacbonatCc thnh to Cacbonat Vit Nam c tui t Ordovic Silur n Trias- Cc tng cha nc h Trias phn b thnh mt di ln ko di theo hng Ty Bc ng Nam, vng Ty Bc Bc B, chim din tch khong 1.200km2, thuc cc tnh Lai Chu, Sn La, Thanh Ha, Ninh Bnh. Cc tng cha nc khe nt Karst paleozoi phn b kh rng nhiu vng thuc Bc B nh Qung Ninh, Cao Bng, Lng Sn, Bc Cn, Thi Nguyn, Tuyn Quang, Sn La, Lai Chu, Thanh Ha. t cha nc l vi phn lp dy, nt n, hay hang hc Karst pht trin. Nhn chung, y l nhng tng cha nc phong ph. Cht lng nc tt, nc thng c dng Bicacbonat Clorua hoc Bicacbonat Sunlfat, tng khong ha 0,3 0,7g/l. Cc tng cha nc ny c th p ng yu cu khai thc cung cp nc vi quy m va n ln.- Cc thnh to Cacbonat h Ordovic Silur c din phn b hp, c th gp mt s vng thuc Ty Ngh An, H Tnh, Qung Bnh, Qung Tr, in Bin, Lai Chu Thnh phn ch yu l cc lp hoa mng, mc nt n v Karst ha yu nn cha nc ngho.

2.3.5. Cc thnh to a cht rt ngho nc hoc khng cha nc

Bao gm cc thnh to lc nguyn, lc nguyn phun tro h Paleogen Neogen (P-N), h Jura Creta (J3 K1) v h Trias. Thnh phn thch hc ch yu l st kt, bt kt, phin st, phun tro Ryolit, Spilit, Dacit. Cc thnh to bin cht Cambri Ordovic (C O). Proterozoi (PR) v Arkeozoi (AR). t ch yu l phin thch anh mica, phin Amphibolit, Quarzit, GneisCc thnh to ny phn b rng vng Bc B, Ty Bc B, Bc Trung B v Ty Nguyn.

Nhn chung, cc thnh to a cht ny rt ngho nc. Cc l khoan thng khng c nc hoc nu c luu lng cng t khi vt qu 1l/s. Tuy nhin, cc t gy kin to hnh thnh cc i ph hy kh phong ph nc, chng c th l i tng tm kim nc c trin vng trong cc thnh to ngheo nc ny. Nc trong cc thnh to ny c cht lng tt, tng khong ha thng nh hn 0,3 g/l, nc thng c dng Bicacbonat Clorua.Cc thnh to mc ma xm nhp c cu to khi c sit, rt t nt n nn khng cha nc, nc ch tn ti trong i phong ha pht trin khng dy trn b mt cc khi xm nhp. V ma kh, nc trong i phong ha ny thng b cn kit.CHNG 3

CHT LNG NC NGM

3.1. Tnh cht ca nc ngm

3.1.1. Tnh cht chung

Nc ngm c to nn do ma v hi nc thm vo trong lng t v c gi li trong cc tng tr nc nm xen k vi cc tng khng thm nc. Do nc thm qua cc tng t ct si ging nh qu trnh lc qua cc vt liu lc nc nn nc ngm c hm lng cht l lng nh. Tn ti trong cc tng tr nc l cc khong cht, v vy nc ngm thng c hm lng cc nguyn t kim loi c bit l st m mangan. Hm lng cc nguyn t kim loi trong nc ngm ph thuc vo tnh cht a cht ca tng khu vc. C nhng ni nc ngm sch, bo m cc yu cu ca nc sinh hot v n ung ch phi x l n gin nh kh trng ri a vo mng li tiu dng. Ngc li c nhng ni hm lng st v mangan rt cao, thm ch nc ngm cn c hm lng cc kim loi nng khc nh Cu, Hg, Pb, Cr, v cc hp cht nit amn cn phi qua x l rt phc tp mi c th s dng c. Trong mt khu vc cht lng nc ngm cng khc nhau, v d khu vc pha bc TP. H Ni cht lng nc ngm thng tt hn nhiu so vi pha nam H Ni. Thm ch trong mt nh my nc cht lng nc ca cc ging khai thc cng khc nhau. Tuy nhin, nhn chung cht lng nc ngm thng tt hn so vi cht lng nc mt. V th, nc ngm thng c s dng lm ngun nc cho sinh hot v cng nghip va bo m v sinh va gim c gi thnh x l. c th nh gi c cht lng c th ca nc ngm chng ta i su tm hiu su v mt s tnh cht c bn ca nc ngm.3.1.2. Tnh cht l hc

c ca nc ngm nhn chung nh, nu cng trnh khai thc nc ngm hon thin th cc cht cn th cng khng c trong nc ngm.

Nhit nc ngm thng tng i thp, c bit nc ngm tng su nhit ca nc nc ngm xung ti 7 120C. Bn cnh c trng hp nc ngm c nhit qu cao ti 70 800C (nc khong) ch thch hp s dng cho nhng mc ch cp nc sinh hot v cung cp cho cy trng. Nu nhit nc ngm thp hn 300C hoc cao hn 350C khi s dng cn phi thng qua x l. x l tng nhit , nc ngm t ging bm ln dc tr li trong b hm nng di nh mt tri.

3.1.3. Tnh cht ha hc

Tnh cht ha hc ca nc ngm thng c th hin khong ha ca nc ngm. Nc ngm nhn chung c khong ha cao so vi yu cu cho php s dng sinh hot, n ung v cc mc ch khc. Trong nng nghip nu nng tng s cc cht khong cha trong nc