XN000022-1977-07-04 — Page 4

MONDAY, JULY 4, 1977

3 L

QUOTING AN EXAMPLE, MR. WONG SAID RESERVOIR STORAGE FIGURES SHOWED THAT, FOLLOWING OUR DRIEST WINTER ON RECORD, SOME 75 MM (3 INCHES) OF THE INITIAL RAINS OF MAY ADDED VIRTUALLY NOTHING TO THE RESERVOIRS, BECAUSE THEY WERE SOAKED UP BY THE SOIL.

+THIS SOAKING PROCESS MUST REACH FULL SATURATION LEVEL BEFORE EXCESS WATER WILL FLOW OVER THE CATCHMENTS INTO THE RESERVOIRS,+ HE SAID.

+THE FACTS ARE THAT THE FIRST COUPLE OF INCHES OF RAIN FALLING INTO DRY EARTH GIVE VIRTUALLY NO YIELD AT ALL.

THE NEXT INCH OR TWO WILL ONLY BEGIN TO PRODUCE WATER YIELD TO THE RESERVOIRS IF THE RAIN HAS BEEN UNINTERRUPTED AND QUITE HEAVY.

+ONLY AFTER AT LEAST 152 MM (6 INCHES) OF ALMOST CONTINUOUS RAIN HAS FALLEN ON THE CATCHMENT AREAS DO WE BEGIN TO GET TO A STAGE WHERE MOST OF THE RAIN IS RUNNING DIRECTLY TO THE RESERVOIRS, SUBSTANTIALLY BOOSTING OUR WATER STORAGE.

+AND IN RECENT MONTHS WE SIMPLY HAVEN'T BEEN GETTING MANY STEADY AND PROLONGED DOWNPOURS AND CERTAINLY NONE

IN THE CATCHMENT AREAS WHERE WE NEED THEM.

+WHAT WE BADLY NEED NOW IS A SERIES OF HEAVY AND PROLONGED TERRITORY-WIDE RAINSTORMS, OR EVEN THE OUTER RAIN BAND OF A PASSING TYPHOON.

MR. WONG SAID THAT FOR THE PAST 24 YEARS, HONG KONG'S RAINFALL DISTRIBUTION PATTERN HAS BEEN ANALYSED FROM RECORDS MADE AT ROYAL OBSERVATORY RAIN GAUGES, NOW TOTALLING 140 AND LOCATED THROUGHOUT HONG KONG.

THIS NETWORK OF GAUGES IS READ EACH DAY BY OBSERVATORY PERSONNEL, WATER SUPPLIES DEPARTMENT ENGINEERS AND AN ARMY OF POLICEMEN, SCHOOL CHILDREN AND OTHER PUBLIC VOLUNTEERS.

+ALL RECORDS THIS YEAR SHOW THE SAME THING -- AN ABNORMAL RAIN PATTERN,+ SAID MR. WONG.

+OF THE RAINFALL FOR JUNE, FOR EXAMPLE, ONLY 74 PER CENT FELL OVER THE ENTIRE CATCHMENT AREAS, WITH SOME RESERVOIRS, LIKE SHEK PIK, RECEIVING ONLY 55 PER CENT.+

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HONG KONG'S +GROUND WATER LEVEL+ WHICH INDICATES THE AMOUNT OF RAINFALL WHICH WILL STILL BE ABSORBED BY THE SOIL AND THEREFORE WASTED - IS CHECKED AT A NUMBER OF OBSERVATION WELLS ON THE HIGH ISLAND AND OTHER CATCHMENT AREAS, AND FROM REPORTS BY PRIVATE WELL OWNERS ELSEWHERE THROUGHOUT THE NEW TERRITORIES.

THE LEVEL ROSE SLIGHTLY DURING JUNE, BUT MR. WONG WARNED IT WAS STILL VERY LOW FOR THIS TIME OF YEAR, AND THAT ABSORPTION OF RAINFALL BY THE SOIL IS STILL EXPECTED TO BE HIGH.

+UNTIL THE MOISTURE CONTENT IN THE SOIL REACHES ITS NORMAL LEVEL, THE CATCHMENTS WILL STILL NOT GET THE FULL BENEFIT OF RAINS, HE SAID.