WATER RESOPRCES RESEARCH CENTER UNIVERSITY OF HAWAII INFRARED EXPLORATION FOR HAWAIIAN GROUND WATER COASTAL SPRINGS

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1 Memorandum Report No. 8 WATER RESOPRCES RESEARCH CENTER 2525 Correa Road UNIVERSITY OF HAWAII Honolulu, Hawaii INFRARED EXPLORATION FOR HAWAIIAN GROUND WATER COASTAL SPRINGS A Status Report, 10 December 1966 by Leonard A~ Palmer February 1967

2 INFRARED EXPLORATION FOR HAWAIIAN GROUND WATER A Status Report, 10 December 1966 COASTAL SPRINGS INTRODUCTION Ground water springs near the shoreline discharge a large portion of the Ghyben-Herzberg fresh water lens in the Hawaiian Islands. Conventional methods are applicable to measurement of rainfall, evaporation and runoff, but the irregular distribution and size of holes in the volcanic rock through which most Hawaiian water flows make accurate ground water flow measurements difficult (Fig. 1). More precise information on the rates of ground water losses through coastal spring discharge are important to the understanding and planning for future Hawaiian water supply. Numerous infrared sensing instruments and infrared sensitive films h.y~ recently been developed. A variety of reliable and economical methods of utilizing infrared radiation and reflection are being successfully applied to the study of rocks, plants, sea water and other material (Fischer, 1964; Gates and Tantraporn, 1952; Gates, 1959; Smith, 1956). Specifically, infrared radiation has been shown to be an effective indicator of fresh and sea water temperatures (Clark and Frank, 1963). A side result of infrared radiation studies of Hawaiian volcanoes with imaging radiometers was the detection of coastal springs ground water into the sea around the island or Hawaii. The temperature contrast between cool or warm ground water and sea water was detected showing 219 springs on the periphery of that island (Fischer et al, 1964 and 1966). (Fig. 2). Such springs have long been known to exist and were utilized even by ancient Hawaiian settlements. Many of the larger spr.lngs are easily recognized, and some have been developed for use, as in the Pearl Harbor area. However the smaller and more diffuse flows are not easily recognized. Infrared measurements potentially permit much better recording of the locations and relative strengths of the coastal springs. The imaging radiometers utilized by Fischer et al are "temperamental and difficult to operate without thorough training" and are expensive to procure and operate (Fischer, personal communication, 1966). More reliable and economical infrared sensors are available but their adaptation to Hawaiian coastal spring detection has not previously been attempted although they have qeen used by the U. S. Geological Survey in other areas (~rown.;~personal communication, 1966). A joint federal and state project funded for the year through the Water Resources Research Center at the University of Hawaii in part will investigate the applicability of various sensors to the measurement of thermal contrast in and around coastal ground water springs

3 Figure 1. Groundwater flow in the Hawaiian Islands is difficult to measure partly because of the irregular distribution and size of holes in the volcanic rocks through which the water passes. This photo shows the water flow into the liwau Tunnel, Waiahole, Oahu, Hawaii.

4 -4- wasting into the sea (Office of Water Resources Research Project No. B-005-HI,"Geophysical Exploration for Hawaiian Ground Water"). Studies will include the examination of infrared radiation spectra at various wavelenghts by films and thermistor instrumentation. Surface and underwater temperatures will be compared with radiometer measurments to determine the accuracy and water penetration of radiation sensors. From thermal radiation characteristics and their measurement, analysis will be made of the techniques for their application to coastal spring detection and to other ground water research. PROCEDURE The infrared study will involve the following steps:,.. 1. Pr>oaurement and laboratory aazibration of instrumentation: Photo sensitive infrared and panchromatic films will be tested under varying conditions of water salinity, temperature and surface roughness with various filter combinations to pass selected light spectra. Reflectivity and possible thermal radiation effects will be studied. Infrared radicmetric measurements will be tested in various wavelength passbands to about 15 microns including use of the thermistor bolometer infrared thermometer manufactured by Barnes Engineering Company. Test will be concurrent with and include parameters tested with films above. Water temperatures of the tests will be varied using more conventional expansion and thermistor temperature measuring apparatus. Temperature thermocline effects will be evaluated to determine the "skin temperature" and depth of penetration of thermal measurements by the above methods A Barnes Engineering Company Model IT-3 infrared thermometer has been obtained and is being tested for temperature calibration, response rate and stability (see Fig. 3). Initial tests suggest that it will be adaptable to scan the sea surface at a rate of about 40 miles per hour from an altitude of 200 feet. Panchromatic, orthochromatic and infrared sensitive films are being tested with various filter arrangements. Thermal sensitivity of the films is too low to be useful in most field conditions. Initial findings indicate that their primary utility will be documentation of Thermistor radiometer survey areas and study of sub-sea surface topography in shallow areas. 2. Surfaae field testing: Known ground water coastal springs are being examined from shore and from a boat by photosensitive infrared films, thermistor bolometer, and underwater thermistor thermometer andsalimometer to determine reflective, thermal radiation, and water temperature parameers. Tests of water salinity and temperature have been done in areas of known spring discharge using a conductivity bridge and thermistor temperature

5 BARNES ENGINEERING' COMPANY rjiodel IT-3 INFRARED THERMOMETER,. ",: ", ;"r ',' -~ t '. 1."he ModellT-3 Infrared Thermometer'meas ~res the temperature of materiais, hot, or

6 -6- over a total span from -50 to F: A special cast-metal sensing head cover is available for permanent installations when it is desirable to air-purge to maintain cleanliness; cooling coils may be installed within this head to protect the IT-3 sensing elements from high ambient temperatures. All components of the IT-3 are contained within the electronics case and two metal end covers when the instrument is stored or transported. A swiveling carrying handle folds under the electronics case to incline,the control panel and meter at an angle convenient for operation and reading. ELECTRpNICS CONSOLE An illuminated push-button on-off switch and a response speed selector are the only controls used in normal operation. For convenience, a protective fuse is also panelmounted. Special modifications of the IT-3 are available for specific application to difficult measurements, such as determining the temperature of thin, moving films of plastic. The Applications Engineering staff of the Instrument Division welcomes the opportunity to discuss the applicability of the IT-3 in nonstandard areas. STANDARD SENSING HEAD SPECIAL AIR-COOLED SENSING HEAD ft-3 SPECIFICATIONS TEMPER~TURE RANGES Type ' Range 2 ReSOlution Absolute Accuracy] ----t t t A - 40 C to + 60 C 0.5 C (above 0 C) 2 C (above 0 C) - 50 F to F 1 C (below O C). 4 C (below O C) B + 60 C to C O,70C F to +400 F 2.5 C E + 100C to + 60 C 0.5 C 1.2 C + 50 F to F S -looc to +45 C + 100F to + HO F 0.5 C 1.2 C NOTES: 1. Other temperature ranges optional at extra cost. 2. Each type is calibrated in both Centigrade and Fahrenheit. 3. Accuracy is stated for target emissivity of unity. Field of View "', Response Time Readout Recorder Output Spectral Passband Ambient Temperature Power Required Cables Weights 3 (0,70 or 30 optional), focussed at infinity (close-focussing optional). "Fast" mode: 50 milliseconds to 63%. "Slow" mode: 500 milliseconds to 63%. Degrees Centigrade and Fahrenheit direct on meter face. 50 millivolts full-scale adjustable, 1000 ohms. 8 to 14 microns standard; (other bandwidths on special order). Specified accuracy is maintained in ambients from + 40 F to F for Type A and Type E; + 40 F to + HO F for Types Band S. Operable in ambients down to O F with slight degradation of accuracy. (Head casting with water cooling coils optional.) 105 to 125 volts, 58.7 to 61.3 cps, 25 watts. (50 cps optional.) Power and interconnecting cables; 8 feet long. Longer interconnecting cable optional. Optical Head, 2 3,4 pounds Electronics Console, pounds Complete Instrument (with covers and cables), 20 1 /2 pounds Shipping Weight, 30 pounds Fig. 3.

7 -Treading from a Beckman RB3-334l Solu Bridge as well as mercury bulb thermometers. Tests in the Pearl Harbor East Loch and West Loch indicate that the discharge of springs may be variable depending on seasonal, climatic and diurnal changes of ground and surface water flow. Examination of coastal springs on the island of Hawaii is now underway to test the temperature and salinity of areas located by Fischer et al (1966) using infrared aerial scanning techniques. 3. Aerial, fie Ld testing: Ground water coastal springs will be examined by aerial infrared photographic and thermistor bolometer instrumentation using vario~s wavelength bandpass and scanning techniques from an airplane. Conventional aerial photography will be used in conjunction with infrared sensors as a reference to location of measurements. Arrangements are in progress with the Hawaiian Army National Guard to obtain helicopter flight time for infrared thermistor bolometer surveys. Early tests are planned for January Magnetic tape recording of the D.C~ Voltage readout from the radiometer is being assembled utilizing a cartridge type tape transport with special accessory FM signal recording electronics installed. Magnetic tape data recording will provide versatility in readout of the temperature data including either true temperature readings or intensity modulated readout to provide imaging capability. 4. CompiZation and r>orrrparat:.i,.,o evaluation: Results of various thermal sensor te~nnlques will be compiled and compared to determine best applicabilitr ror coastal spring detection and description. 1. A. Palmer

8 -8- REFERENCES Fischer, W. A., D. A. Davis, and T. M. Sousa (1966) Fresh-water springs of Hawaii from infrared images. U. S. Geological Sux'vey Hydrologic Investigations Atlas HA Fischer, W. A., R. M. Moxham, F. Polcyn, and G. H. Landis (1964) Infrared surveys of Hawaiian volcanoes. Science 146(3645):