XN000022-1977-07-07 — Page 5

THURSDAY, JULY 7, 1977

IN ADDITION TO THE RAIN GAUGE AT THE ROYAL OBSERVATORY, THERE ARE ANOTHER 139 RAIN GAUGES IN HONG KONG AND THE NEW TERRITORIES. MANY OF THESE ARE WITHIN CATCHMENT AREAS SO THAT THE DISTRIBUTION OF RAINFALL OVER THE ENTIRE AREA IS FULLY RECORDED.

NORMALLY ONLY THE RAINFALL READING AT THE ROYAL OBSERVATORY IS MADE KNOWN TO THE PUBLIC. BUT, MR. WONG SAID, +IN VERY EXCEPTIONAL CIRCUMSTANCES LIKE THOSE WE EXPERIENCED IN MAY AND JUNE THIS YEAR, WHERE THERE WAS A BIG DIFFERENCE BETWEEN THE AMOUNT OF RAINFALL RECORDED IN THE ROYAL OBSERVATORY AND WHAT WAS RECORDED IN OTHER LOCATIONS. THE WATER SUPPLIES DEPARTMENT WAS ABLE TO USE THE RECORDINGS MADE ON THE 139 OTHER GAUGES TO EXPLAIN THE DISPARITY TO THE PUBLIC.+

EACH MORNING ABOUT 300 READINGS ARE TAKEN AT SERVICE RESERVOIRS, FILTER STATIONS, AND PUMPING STATIONS SO THAT WATER CONSUMPTION CAN BE CALCULATED.

IN ADDITION TO THE DAILY CONSUMPTION, THE DATA FROM WATER BILLS IS UTILISED TO CALCULATE DOMESTIC, TRADE, BUILDING, SHIPPING, AND OTHER CATEGORIES OF CONSUMPTION.

EACH CATEGORY OF CONSUMPTION IS THEN PROJECTED TO GIVE THE FUTURE ESTIMATED DEMAND.

MR. WONG TOLD HIS AUDIENCE THAT THE CHARACTERISTICS OF EACH CATCHMENT DETERMINE HOW MUCH YIELD THERE IS FROM ANY RAIN WHICH FALLS THERE.

+WHEN RAIN FALLS, THERE ARE TWO WAYS IN WHICH IT CAN DISPERSE. IT CAN EITHER SOAK INTO THE SOIL AND GET LOST INTO THE GROUND - LIKE FALLING WATER ON SAND OR FLOW OVER THE LAND INTO THE RESERVOIRS WHEN IT IS WITHIN CATCHMENT AREAS.+

MR. WONG SAID THAT THE PROPORTION OF WATER WHICH IS LOST THROUGH THE GROUND AND THAT WHICH FLOWS INTO THE RESERVOIR DEPENDS ON A NUMBER OF FACTORS.

THESE INCLUDE THE NATURE OF THE GROUND, ITS MOISTURE CONTENT, THE GROUND WATER LEVEL AND SUB-SOIL CONDITIONS, VEGETATION, WHETHER THE LAND IS STEEP OR FLAT, AND THE QUANTITY OF WATER REQUIRED BY VILLAGERS TO IRRIGATE THEIR FIELD. THE IR NEEDS ARE GIVEN PRIORITY.

ANOTHER FACTOR AFFECTING THE AMOUNT OF WATER THAT CAN BE COLLECTED IS THE PATTERN OF RAINFALL ITSELF. +CONSOLIDATED RAINFALL LIKE THAT ASSOCIATED WITH A TYPHOON CAN YIELD MORE WATER TO FLOW DIRECTLY INTO THE RESERVOIRS.

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