Salt-Water Study of the Miami River Dade County, Florida
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STATE OF FLORIDA STATE BOARD OF CONSERVATION DIVISION OF GEOLOGY FLORIDA GEOLOGICAL SURVEY Robert O. Vernon, Director REPORT OF INVESTIGATIONS NO. 15 SALT-WATER STUDY OF THE MIAMI RIVER AND ITS TRIBUTARIES, DADE COUNTY, FLORIDA By S. D. Leach and R. G. Grantham U. S. Geological Survey Prepared by the UNITED STATES GEOLOGICAL SURVEY * in cooperation with DADE COUNTY and THE FLORIDA GEOLOGICAL SURVEY 1966 FLORIDA STATE BOARD OF CONSERVATION HAYDON BURNS Governor TOM ADAMS EARL FAIRCLOTH Secretary of State Attorney General BROWARD WILLIAMS FRED O. DICKINSON, Jr. Treasurer Comptroller FLOYD T. CHRISTIAN DOYLE CONNER Superintendent of Public Instruction Commissioner of Agriculture 1i LETTER OF TRANSMITTAL W1 Jforida Ljeoloyical Survey Tallahassee August 16, 1966 Governor Haydon Burns, Chairman State Board of Conservation Tallahassee, Florida Dear Governor Burns: Messrs. S. D. Leach and R. G. Grantham, of the Water Resources Division of the U. S. Geological Survey, have completed a study of the Miami River and its tributaries in Dade County, and the relationships of these tributaries to salt-water intrusion in the area. The report will be published as Report of- Investigations No. 45. The study was done in cooperation with the Division of Geology, of the State Board of Conservation, and Dade County, and outlines the main trend of the water resources of the Miami area. The Biscayne aquifer, which is composed of highly permeable limestone, is being intruded upon by salt water along any canal or stream that connects the aquifer to salt water. It has been found that this intrusion could be prevented and reversed by careful management of the water resources of the area by the construction of salinity control dams near the coast, and through the judicious development of water. Respectfully yours, Robert O. Vernon Director and State Geologist iii Completed manuscript received August 16, 1966 Published for the Florida Geological Survey By Rose Printing Company Tallahassee 1966 A»; CONTENTS Page Abstract ---.-----------.-------. ----. ....-...-.....--......---.. 1 Introduction ..--.- ---..---..--..--. ..-.--.- . ---------------......--...........-........ 2 Area of investigations .--.............---.... ---....... ... ..---..... .....-. ...-.. .......-- ... 4 History of salinity-control dam operation in the Miami Canal --...---..... 6 Rainfall in the Miami River drainage basin ...-----... --------...............-------- 8 Long-term hydrology ...................--------------...........------- ..----------- 9 Discharge in the Miami Canal ---....-............ .------.-.........-..---..--...--- 9 Water levels in the area of investigation --..--..-..--.....-----..--.......--......--.. 10 Water-level comparison between Miami River and Biscayne Bay ....---.. 11 Salt-water movement in the Miami River ----------- --------- -------- 14 Short-term comparison of chloride with water levels and discharge .--.-- 19 High and low tide salt-water movement ..........-........---.-------- .-----. 23 Chloride concentration extremes --.......-------------..--------...---. 23 The 1945 drought -..--- _ .--......------ ___.....---.-------------. ------ 25 Chloride concentration in the aquifer .........---.------------------- 25 Discharge at selected locations .------...--. ....-----------.------- 28 The effects of wind on water movement -----...----.....-------------..---..--- 31 Summary -----.--- ............-------...----------------.--........... 33------------3 References .----........... -------------------- ------------- 35 ILLUSTRATIONS Figure Page 1 Map of the Greater Miami area showing the major canals and the area investigated ..--...----.........-----..--.. -------------...............---- 4 2 Map of the Miami River and its tributaries showing data-collection sites in the area investigated ................-........--------------............ 5 3 Photographs of successive salinity-control dams in the Miami Canal at N.W. 36th Street ........--------.....-..---.--.......... ---.-----... ----------------. 7 4 Graph of monthly mean rainfall, monthly extremes, and the year the extremes occurred based on the averages of Hialeah, Pennsuco, and Pennsuco 5 N.W. (Broken Dam) rain gages for the period 1944 through 1963 .-..---.... .--......----...---------- . ....------..---..-- ----- 8 5 Graphs showing monthly and annual mean discharge in the Miami Canal above N.W. 36th Street control dam and the total an- nual and monthly rainfall for the three rain gages in the Miami Canal drainage basin --........---...........................------ --------. ..-----...--- 9 6 Graphs of water levels at three selected Miami Canal stations and one Biscayne Bay Station, from 1944 to 1963 ---__---.-------------- 11 7 Hydrographs of monthly high, low, and average water elevations in the Miami Canal at N.W. 27th Avenue and at Biscayne Bay, based on 18 years of record'1946 to 1963 ....-.....................-------------......---- 12 8 Graphs showing a mean water-level elevation, mean high and low water from the N.W. 36th Street control dam to the mouth at Bis- cayne Bay, based on 18 years of record 1946 to 1963 ....---.-......---- .. 13 9 Graph showing percentage of time water containing 1,000 ppm chloride was at or above various locations in the Miami Canal for the period May 1945 to March 1958 -......--..........-------............ ----- 15 V ILLUSTRATIONS Figure Page 10 Graphs showing position of the 1,000 ppm chloride content in the Miami Canal for the period January 1940 to March 1958 .---........---. 16 11 Graph showing relation between monthly mean discharge in cfs and the location of water containing 1,000 ppm chloride in the Miami Canal ..............--.... ..... .... .............---------------------.................. .......................-- 17 12 Graphs showing chloride concentration in the Miami Canal during a typical wet year (1948) and a typical dry year (1956) .............. 18 13 Graphs showing the effect of changes of the N.W. 36th Street con- trol dam on discharge,water levels, and chloride content at selected locations in the Miami Canal from July 12 to 19, 1964 ..--..-.........--. 20 14 Graphs showing the effect of changes of the N.W. 36th Street con- trol dam on discharge, water levels, and chloride content at selected locations in the Miami Canal during the period August 14 to 19, 1964 .......................-.... -......---------------........... --............- ....- --.....--- ......-----21 15 Profile of chloride content in the Miami Canal on July 16, 1964 at low and high tide when the N.W. 36th Street control dam was par- tially open .--- --.....--........ --. --.. ....... ...--.......--. .--.-------------- 22 16 Graphs showing chloride extremes at high tide in the Miami River and the Miami Canal at various sampling locations ........--------...... 24 17 Graphs showing an extreme chloride concentration in the Miami Canal above the N.W. 36th Street control dam on May 31, 1945 ... 26 18 Map showing salt-water encroachment at the base of the Biscayne aquifer 1904-62 (Parker and others, 1955, p. 589), (Kohout, 1961) updated ..- .-......................... .....-.--........ ............... ..-............-..........-......-... 27 19 Graphs showing monthly mean discharge at selected locations in the Miami and Tamiami Canals, October 1960 through September 1963 .--...-........... .......-................-..--..--......-- .................................................. 29 20 Graph showing monthly mean discharge from or into the aquifer below the control dams in the Miami River and its tributaries, April 1961 through September 1963 ...............------------------.........................-- 30 21 Graphs showing the effects of Hurricane Cleo's winds at selected discharge and water-level stations in the Miami Canal and Bis- cayne Bay, August 26-27, 1964 -........----.............------ ..--- ----- 32 vi SALT-WATER STUDY OF THE MIAMI RIVER AND ITS TRIBUTARIES, DADE COUNTY, FLORIDA By S. D. Leach and R. G. Grantham ABSTRACT The main threat to water resources in the Miami area is salt- water intrusion into the highly permeable Biscayne aquifer. Saltwater pollution of the aquifer may be held at its present loca- tion or moved seaward by raising the fresh-water levels in the ground by increasing fresh-water heads behind the control dams, or by moving the controls farther downstream in the canals. Analysis of available data indicates that water containing 1,000 parts per million or more of chloride in the Miami Canal is immediately downstream from the salinity-control dam at N.W. 36th Street approximately 23 percent of the time and at N.W. 27th Avenue about 60 percent of the time. Also, an analysis of flow data indicates that when the discharge of the Miami Canal at N.W. 36th Street is approximately 280 cubic feet per second or less, the salt-water wedge is located at the downstream side of the control dam at N.W. 36th Street. With the present location of the control dams a minimum discharge of 550 cubic feet per second would be required to hold the salt-water wedge downstream from N.W. 27th Avenue. The fresh-water discharge from 60 percent of the aquifer in the Miami River and its tributaries below the control dams would be salvaged by moving the controls downstream from the con- fluence of the Tamiami Canal. With reference to proposed downstream locations of controls, it was determined that during dry years, as experienced in 1961-62, there would be a discharge of about 55 cubic feet per second available for boat lockages in the Miami Canal at N.W. 27th Avenue