NOTE ON ^HE TIDAL VARIATION OF SPRINGS AND DEEP 

 WELLS IN THE PHILIPPINE ISLANDS i 



By George W. Heise 



(From the Laboratory of General, Inorganic, and Physical Chemistry, 

 Bureau of Science, Manila, P. I.) 



Throughout the Philippines there are many springs, located 

 near the coast, whose flow is greatly affected by the tides. Some 

 of them, situated on the beach, are completely covered at high 

 tide, so that to get water from them one is obliged to wade 

 into the ocean and catch the fresh water as it issues from the 

 sands. Many drilled wells show a great tidal variation in quan- 

 tity of water. For example, the well at Bauan, Batangas, 90 

 meters deep, flowing 190 liters per minute at low tide, has a 

 flow five times as great (950 liters) at high tide. Some, as in 

 the case of several located at Iloilo, flow at high tide, but must 

 be pumped at low water. 



With all this variation in quantity of water, there is very 

 little, if any, change in quality. This is quite to be expected, 

 since the natural flow of subsoil water is toward the sea, generally 

 under pressure great enough to prevent the admixture of sea 

 water. A number of flowing wells in Iloilo, which yield brackish 

 waters in quantities varying greatly with the tides, showed no 

 appreciable change in quality, and because of their peculiar 

 composition (high chlorine content and absence of sulphates 

 and occasionally of calcium salts), entrance of sea water was 

 practically out of the question. 



A spring at Punta Oslob, Cebu, was described by Abella,* 

 as follows: 



It emerges and flows over the beach in the zone which is alternately 

 submerged and uncovered by the tides, and its waters, which are salty when 

 the mouth of the spring is not covered by the sea, are, on the other hand, 

 perfectly sweet when it (the spring) is covered at high tide. In consequence 

 the inhabitants who use this water for drinking, await high tide to fill 

 their 'bambones' (bamboo tubes) or jars, holding them in the whirl or 

 eddy which the sweet water produces in the supernatant sea water. 



Abella offers the suggestion that there may exist a cavity in 

 the rocky structure of the beach in which water collects at high 

 tide, discharging into the spring and contaminating the water 

 at low tide. 



' Received for publication December 6, 1915. 



' Rapida descripcion * * ♦ de la isla de Cebu. Madrid (1886), 87. 



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