III. Resultados
3.2. Identificación de los puntos críticos
3.2.1. Normas Legales de Distribución de Medicamentos
o
I
*000I
ê1
>900. WHITE LAGGAN 900. 0. «000. CQ CL S:.I
I
o 14000. 1*000. 10000.D ilu tio n gauging in v o lv e s th e in je c tio n e ith e r a t a c o n sta n t r a te or as a "gulp" ( ie . a s in g le in sta n ta n e o u s in p u t) o f a chem ical in th e stream %Aich a f t e r a long enough d ista n c e downstream to allow thorough m ixing, i s sampled and th e c o n c e n tra tio n of th e chem ical d eterm in ed . The c o n c e n tra tio n of th e chem ical in th e sam ples i s used to c a lc u la te th e d ilu tio n and hence d isc h a rg e . The method of d ilu tio n gauging employed a t Loch Dee i s th a t used by th e I n s t i t u t e of H ydrology, Systems Group. T his method in v o lv e s in je c tin g a known volume of sodium io d id e tr a c e r in to th e stream as a g u lp in je c tio n (shown in p la te XIV) and ta k in g sam ples a t a d ista n c e between 50-160 m etres downstream. T his io d id e method h as an advantage over o th e r d il u tio n te ch n iq u es in th e in c o rp o ra tio n of an io n s e le c tiv e e le c tr o d e . The e le c tro d e i s flo a te d in th e stream a t th e sam pling p o in t (coupled to a m eter and c h a rt re c o rd e r on th e bank), t h i s d e te c ts th e passage of th e io d id e p a st th e sam pling p o in t. P la te XV shows th e use of t h i s method on th e Green Burn. From th e c h a rt reco rd from th e io n s e le c tiv e e le c tro d e one can judge th e sam pling frequency n ece ssary in o rd e r to c h a ra c te ris e th e range and d is tr i b u tio n of c o n c e n tra tio n s w h ils t conserving th e number of sam ples tak en .
F ig . 4:6 shows th e c o n c e n tra tio n s of io d id e through each of th e gaugings on th e th re e stream s. In o rd er to c a lc u la te stream d isch arg e th e d a ta a re m anipulated in th e following eq u atio n :
Q =
[
( C 2 - C o ) d t(Gilman, 1977)
Where Z i s th e volume of th e in je c te d s o lu tio n .
Cl i s th e c o n c e n tra tio n of th e in je c te d s o lu tio n .
C2 i s th e observed c o n c e n tra tio n of tr a c e r a t th e sam pling s t a t io n and
Co i s th e background c o n c e n tra tio n in th e stream (assumed to be c o n s ta n t) .
The r e s u lt s of th e d ilu tio n gauging un d ertak en in th e th re e stream s a re g iv e n in ta b le 4 :3 . The r e s u lt s show th a t d ilu tio n gauging c o n s is te n tly g iv e s a h ig h e r d isch arg e th an th a t o b tain ed from
th e r a tin g r e la tio n s h ip from c u rre n t m eterin g . S ta tio n D a rg a ll Lane Whi te Laggan Green Burn R ated C u rren t M eter Gauging (m3s ■*’) 0.016 0 .0 2 2 0 .0 1 6
D ilu tio n Gauging (m^s“ ^)
0.017 0.027 0.021 Table 4 :3 Comparison of R ated C urrent M eter Gauging
The d iffe re n c e s between th e two s e ts of r e s u lt s a re a ttr ib u ta b le to two re a so n s. F i r s tl y , g iv e n th e very low flow s being d e a lt w ith , c u rre n t m eterin g i s a t i t s m ost in a c c u ra te where v e l o c iti e s of stream flow a re low and v a r ia b le a c ro s s th e stream w idth. The p ro p o rtio n a lly g r e a te r boundary e f f e c t s of th e stream bed and banks a ls o a c t to c re a te v a r ia b le tu rb u le n c e which can g e n e ra te e r r o r s in th e m easurem ent p ro c e ss. D ilu tio n gauging av o id s such e r r o r s and w ill work e f f i c i e n t l y g iv e n a long enough channel le n g th to en su re com plete m ixing o f th e io d id e tr a c e r . However d ilu tio n gauging may in tro d u ce e r r o r s through in fre q u e n t sam pling and a n a ly tic a l e r r o r or more lik e ly through th e p resence of s la c k w a te r between th e in je c ti o n and sam pling p o in ts p re v e n tin g a thorough m ixing of th e tr a c e r .
A second source of d iscrep a n cy between th e methods used occurs as a r e s u l t of th e r a tin g r e la tio n s h ip s developed a t Loch Dee. The number of gaugings a t th e extrem es of flow on a l l th re e stream s i s r a th e r lim ite d g iv in g r i s e to a le s s w e ll-d e fin e d r a tin g r e la tio n s h ip under th e s e flow s and d is c re p a n c ie s between m ethods of measurement may be ex p ected a t th e se flow s. Given th e se d i f f i c u l t i e s th e two s e ts of gauging d a ta g iv e n in ta b le 4 :3 compare rem arkably w e ll.
I t i s lik e ly th a t n e ith e r method of flow measurement d escrib ed h e re i s id e a l under th e f u l l range of flow s a t Loch Dee, however w ith th e p re s e n t re so u rc e s and technology a t Loch Dee th e se tech n iq u es p rovide th e b e s t e s tim a te of stream d isc h a rg e a v a ila b le .
PLATE XX The float-operated chart recorders for the
continuous measurement of water level in
g :
PLATE XXII The continuous water level and water quality
monitoring station on Dargall Lane
PLATE XXIII
The continuous water level recorder on Green Burn
PLATE XXIV
The continuous water
quality station on the Green Burn showing the permanently immersed pH electrode
W ater q u a lity (pH and o o n d u c tiv ity ) in th e stream s has been m easured in W hite Laggan sin c e e a rly 1981 by th e SRPB. With th e involvem ent of th e au th o r in th e p ro je c t in 1983 s im ila r system s were bought and in s ta lle d in th e Green Burn and D arg all Lane catchm ents.
The system a t each s i t e c o n s is ts of a PH OX s e r ie s 57 m k.II c o n d u c tiv ity m eter and a PH OX s e r ie s 47 m k .II pH m eter, shown in p la te XXV. These system s a re powered by 6v rech a rg a b le b a t te r ie s and reco rd onto * R ustrak* p aper s t r i p c h a rt re c o rd e rs o p e ra tin g a t a speed of 6-7
mm hr w ith th e c h a rts la s t in g fo r 3 months. Both pH and
c o n d u c tiv ity a re a u tc m a tic a lly tem p eratu re compensated to th e stan d ard
re fe re n c e tem p eratu re o f 25°^. The system s a re housed in
•w e a th e r-p ro o f* boxes on th e stream banks w ith th e probes perm anently immersed in th e stream s a tta c h e d to a wooden stak e d riv e n in to th e stream bed. The pH probe c o n s is ts of a R u sse ll pH CE7L/NH g e l f i l l e d com bination e le c tro d e (co m p atib le to th e la b o ra to ry model) and i s p ro te c te d by a p la s t ic guard. In th e W hite Laggan Burn and th e D arg all Lane th e w ater q u a lity in stru m e n ts a re alo n g sid e th e gauging s t a t i o n ( p la te s XXI and X X II). However in th e Green Burn th e w ater q u a lity m o n ito rs a re 150m. upstream of th e gauging s ta t io n (p la te s XXIII and XXIV).
The n a tu re of th e w ater q u a lity m easurements d ic ta te s th e g re a te r need f o r m aintenance th an i s needed fo r th e w ater le v e l re c o rd e rs, Pre 1984 th e in stru m e n ts w ere checked weekly (d u rin g th e summer by th e a u th o r) by SRPB p e rso n n e l. Since 1984 and th e appointm ent of a s c i e n t i f i c o f f ic e r (Dr. P.H utchinson) to th e Loch Dee P ro je c t th e in stru m e n ts have been checked on a more fre q u e n t b a s is . A ro u tin e check o f th e in stru m e n ts in v o lv e s checking th e b a tte ry v o ltag e and when low changing th e b a t te r ie s ; tim e checking th e s t r i p c h a rt
re c o rd e rs ; clean in g th e c o n d u c tiv ity probe and clean in g and b u ffe rin g (pH 4 and 7) th e pH probe using sta n d a rd BDH b u ffe r s o lu tio n s su p p lied by th e SRPB la b o ra to r ie s . A re c o rd of a l l ad ju stm en ts, problem s and b a tte ry v o lta g e i s a ls o ta k en . The most common problems w ith th ese type of m onitors appear to be th e v a ria b le speed of th e c h a rt r e c o rd e rs , making a c c u ra te tim e c o rre c tio n im p o rtan t in th e re g u la r check of th e m o n ito rs.
More s e rio u s {a?oblems occur when th e s i t e is in a c c e s s ib le during co ld w in te r p erio d s during which tim e th e b a t te r ie s d ra in very q u ick ly th u s r e s u ltin g in th e lo s s of re c o rd s . In th e summer th e re can be s u b s ta n tia l b u ild up of alg a e on both th e ;Æ[ and c o n d u c tiv ity probes which may d i s t o r t th e re a d in g s. A f u r th e r problem w ith th e pH e le c tro d e s i s th e p e rish in g of th e w a te r - tig h t housing fo r th e e le c tro d e and a ls o th e lim ite d l i f e of th e e le c tro d e s them selves, both r e s u lt in g in th e lo s s of re c o rd s .
4 :3 :4 Q u a lity Co n tro l and D ata R ed u ctio n of th e C ontinuous D ata.
The use of continuous m o n ito rs produces la rg e amounts of d a ta which in th e i r most b a s ic fo rm at may be both bulky and to o d e ta ile d fo r g e n e ra l u se. In o rd e r to reduce th e continuous d a ta in to a more u sa b le and u se fu l form at much of th e d a ta h as been reduced in to a more m anageable form v ia a com puter.
The s t r i p c h a rts a re removed m onthly from th e w ater le v e l re c o rd e rs and 3 monthly from th e w ater q u a lity in stru m e n ts. The c h a rts a r e checked m anually (w a te r le v e l by SRPB and w ater q u a lity , over th e study p erio d by th e a u th o r) fo r re c o rd e r m a lfu n ctio n s and equipm ent f a il u r e . For th e w a te r q u a lity c h a rts cro ss re fe re n c e i s
a ls o made to th e m aintenance re c o rd s tak en a t th e s i t e to determ ine any a d d itio n a l f a u lt s or n o te s which may a f f e c t th e q u a lity of th e re c o rd s . I t i s a t th is s ta g e th a t d a ta a re r e je c te d on one or more of th e fo llo w in g c r i t e r i a :
i . Equipment f a il u r e or mal f u n c tio n - th is i s u s u a lly r e a d ily e v id e n t