Strategies for water quality monitoring

This study provides general guidelines for the preliminary design of a water quality monitoring system. The design is defined as the specification of the parameters to be determined, the number and Location of sampling stations, and the frequency of sampling, The role of several objecrives in the determination of monitoring strategy is considered, The objectives examined are the characterization of stream water quality, enforcement of stream standards and the detection of long-term trends, Principal component analysis is used to identify important water quality parameters and to find the appropriate size of a monitoring network, Information content defined as the reciprocal of the variance of the estimate of the mean concentration is suggested as a valid criterion for the design of a monitoring network for the characterization of water quality, Impact index based on the probability, severity and frequency of violation, number of direct users of the stream water, predominant use and the size of stream is proposed for determining the priority of location in an enforcement network, A protocol for the sampling of non-point sources is presented, The Research Triangle area in North Carolina is used as a case study, A possible framework for the strategy of water quality monitoring is described, This consists of an initial one-time baseline data collection program and eventually three types of networks: (a) an extensive network at relatively large number of key points, (b) an intensive network in selected drainage sub-basins, and (c) a regulation network, TABLE OF CONTENTS ( c o n t i n u e d ) Page . . . . . . . . . . . . . . . . . . . . . . . . . 3.8 S a m p l e S i z e 44 . . . . . . . . . . . . . . 3 .9 Seasona l V a r i a t i o n of Paramete rs 45 . . . . . . . . . . . . . . . . . . 3.10 V a r i a b i l i t y of Paramete rs 46 3 .11 I n f o r m a t i o n Content . . . . . . . . . . . . . . . . . . . . . 47 . . . . . . . . . . . . . . . 3.12 S i z e of t h e Moni tor ing Program 5 1 4 . SPATIAL DENSITY OF STATIONS . . . . . . . . . . . . . . . . . . . 54 . . . . . . . . . . . . . . . . 4 . 1 L o c a t i o n of Sampling S t a t i o n s 54 . . . . . . . . . . . . . . . . . . . . . . . 4.2 L o c a t i o n D e s i g n 56 . . . . . . . . . . . . . . . . . 4 . 3 Number o f Sampling S t a t i o n s 56 . . . . . . . . . . . . . . . . . 4.4 G r a d i e n t L o c a t i o n Technique 56 . . . . . . . . . . . . 4 . 5 I n t e r s t a t i o n C o r r e l a t i o n s Technique 57 . . . . . . . . . . . . . . . . . . . . . . 5 . FREQUENCYOF SAMPLING 6 1 . . . . . . . . . . . . . . . . . . . . . . . SystemDynamics 6 1 . . . . . . . . . . . . . . . Sampling Frequency D i s t r i b u t i o n 63 . . . . . . . . . . . . . . Temporal V a r i a b i l i t y of V a r i a n c e 67 . . . . . . . . . . . . . . . . . . . . . . Frequency Design 68 . . . . . . . . . . . . . . . . . . . . . . Type of Paramete r 69 . . . . . . . . . . . . . . . . . . S t a t i s t i c a l Requirements 69 . . . . . . . . . . . . . . . . . . . . . Averaging I n t e r v a l 70 . . . . . . . . . . . . . S e r i a l C o r r e l a t i o n and P e r i o d i c i t y 71 . . . . . . . . . E m p i r i c a l P rocedure f o r Sampling Frequency 72 6 . VIOLATION DETECTION NETWORK . . . . . . I n t r o d u c t i o n . . . . . . . . . . . Review of P r e v i o u s S t u d i e s . . . . . . . . . . . Ward's Approach . . . . . . Raythesn Approach C r i t i q u e of t h e Proposed Approaches P r o b a b i l i t y of V i o l a t i o n . . . . . L o c a t i o n s of Sampling S t a t i o n s . Mathemat ical Modeling . . . . . . . Segment P r i o r i t y Ranking . . . . . Frequency of Sampling . . . . . . . 7 . SAMPLINGFORTREND . . . . . . . . . . . . . . . . . . . . . . . . 86 . . . . . . . . . . . 7 . 1 Dynamic Nature of Water Q u a l i t y System 86 . . . . . . . . . . . . . . . 7.2 D e c o m p o s i t i o n o f a Time S e r i e s 87 . . . . . . . . . . . . . . . . . . 7 .3 Design of a Trend Network 89 . . . . . . . . . . . . . . . . . . . . . . 7.4 Length of Record 92 . . . . . . . . . . . . . . . . . . . . . . . . 8 . NON-POINT SOURCES 94 . . . . . . . . . . . . . . . . . . . . . . . . 8 . 1 I n t r o d u c t i o n 94 . . . . . . . . . . . . . . . . . 8 . 2 L a n d u s e a n d w a t e r Q u a l i t y 94 . . . . . . . . . 8 . 3 Comparison of Man-made and N a t u r a l Sources 95 . . . . . . . . . . . . . . . . . . . 8.4 R e c u r r i n g Storm Even ts 97 . . . . . . . . . . . . . . 8 . 5 S i g n i f i c a n c e of Non-point Sources 98 TABLE OF CONTENTS (continued) Page . . . . . . . . . . . . . . . 8.6 Estimates of Non-point Sources 100 . . . . . . . . . . . . 8.7 Impact Analysis sf Stormwater Flows 101 . . . . . . . . . . . . 8.8 Sample Surveys of Non-point Sources 102 . . . . . . . . . . . . . . . . 9 . NON-POINT SOURCES: A CASE STUDY 105 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 105 . . . . . . . . . . . . . . . . . . Point Sources and Loads 109 . . . . . . . . . . . . . . . . . . . . . Non-point Sources 111 UrbanRunoff . . . . . . . . . . . . . . . . . . . . . 112 . . . . Variation of Water Quality Within Storm Events 112 . . . . . . . . . . . . . . . . . . . . . RuralRunoff 113 . . . . . . . . . . . . . First Estimates of Non-point Loads 114 . . . . . . . . . . Comparison of Point and Non-point Loads 118 Recommendations for Improving Estimates of Non-point Loads . 118 . . . . . . . . . . . . . . . . . Stormwater Impact Analyses 120 . . . . . . . . . . . . . . Accounting for Benthic Deposits 122 . . . . . . . . . . . . . . . . . . . . . . . 10 . MONITORING STMTEGU 123 . . . . . . . . . . 10.1 Varied Requirements of Monitoring Design 123 . . . . . . . . . . . . . . . . 10.2 One-time Basic Data Program 123 . . . . . . . . . . . . . . . 10.3 Franework of Monitoring Design 124 . . . . . . . . . . . . . . . . . . . ExtensiveNetwork 125 . . . . . . . . . . . . . . . . . . Regulation Network 125 . . . . . . . . . . . . . . . . . . . Intensive Network 126 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . REFERENCES 127 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . APPENDIX 131