區域性自來水供需流布之研究-以臺北縣之鄉鎮市為例

Abstract

臺灣地區年平均降雨量約2,500公釐，換算水量約為905 億立方公尺，是世界平均值（970公釐）的2.6倍，屬降雨豐沛地區之ㄧ；惟受天候、緯度與地形因素影響，不僅季節性之雨量豐枯分布不均，又因河川坡陡流急，以致每年實際可利用水量不及年總降雨量15%，且地小人稠，平均每人每年可分配水量僅約4,250立方公尺，僅為世界平均值（34,000立方公尺）的八分之ㄧ，屬水資源利用潛能不高地區之ㄧ，可供利用的水資源相當有限。 而已獲升格為準直轄市的臺北縣，居住人口位居全國第一，高達380萬人，且仍不斷發展中，如板新特區、新莊副都心等。在水資源有限情境下，如何永續利用應為重要議題。本研究目的是利用物質平衡分析方法，瞭解臺北縣29個鄉鎮市之自來水之實際供需傳輸情況，並探討其供需關係與其應用之課題，讓水資源能有效運用，達成永續利用之目標，供有關機關（臺北縣政府、台灣自來水公司）施政參考。 由研究統計得知，2007年臺北縣行政區人口數3,798,015人、實際供水人口數3,691,998人，其供水普及率為97.21%。其供應臺北縣29個鄉鎮市自來水之供水系統共計有10個，分別由臺灣自來水公司第一區、第二區與第十二區管理處以及臺北自來水事業處等四個單位管轄，並以臺北供水系統與板新供水系統為大宗，兩者合計約佔87.13%。 另研究結果發現，2007年臺北縣自來水總配水量為759,604,162立方公尺，計費水量為517,282,357立方公尺，供水系統之效率為68.10%。若以鄉鎮市來看，供水普及率與城鎮之都市化程度有關，都市化程度越高，其供水普及率較越高。而2007年臺北縣平均之單位供水人口配水量為206立方公尺/年（約每日564公升），平均之單位供水人口計費水量為140立方公尺/年（約每日384公升），均高於每日250公升用水量之國家政策目標。此外，2007年臺北縣無費水量高達242,321,804立方公尺，約為配水量之31.90%，這些無法收取費用之水量，包含有事業用水、消防用水、錶差、管線滲漏及其他（如管線清洗、竊用水量…）等因素，且以管線滲漏為大宗，損漏逾2.4億立方公尺的水量，比同年之石門水庫庫容量2.1億立方公尺還多；若平均每度水以新台幣10元計，僅臺北縣就讓國庫損失高達24億元。 此外，以無費水量的2/3來計算臺北縣29個鄉鎮市2007年之漏水量，估算結果發現，以中和市最高，坪林鄉最低，平均漏水量約為557萬立方公尺，計有中和市(4,081萬立方公尺)、三重市(2,169萬立方公尺)、板橋市(1,377萬立方公尺)、新店市(1,351萬立方公尺)、汐止市(1,244萬立方公尺)、新莊市(993萬立方公尺)、永和市(907萬立方公尺)、淡水鎮(726萬立方公尺)及土城市(601萬立方公尺)等9個鄉鎮市超過此平均值。顯示，都市發展較早之城鎮，其自來水供水管線多已超過使用年限20年，老舊管線造成輸水效率不彰，但為滿足用戶用水需求，加壓加量輸送結果，導致容易發生漏水情勢。然而，如板橋市、新莊市、土城市等城市，隨著都市更新、建物改建，其區域及建築物之供水管線亦進行汰換或新設，對漏水改善有相當助益，值得有關單位考量。

The average annual rainfall in Taiwan is approximately 2,500mm, or 90.5 billion cubic meters a year. As this is 2.6 times that of the world average (970mm), Taiwan can be considered a high rainfall region. The climate, latitude and terrain however meant an uneven seasonal distribution of rain. When coupled with steep, fast-flowing rivers, the actual usable water volume amounts to under 15% of the total annual rainfall. High population density means that each person has just 4,250 cubic meters of water at their disposal – just 1/8 of the world average (34,000 cubic meters). Taiwan is therefore a region with limited water resource potential. Taipei County has now achieved quasi-municipality status and is the most populous region in Taiwan with 3.8 million residents. Development is ongoing as well with new urban planning districts such as the New Banciao Special District and the Sinjhuang Sub-Center. This makes the sustainable use of limited resources a very important issue. The objective of this study is to use material balance analysis to understand the actual situation on supply and demand of tap water in Taipei County's 29 cities and counties. This is then examined to establish the relationship between supply, demand and their applications. The results will go towards ensuring the effective, sustainable use of water and provide the relevant agencies (e.g. the Taipei County Government and Taiwan Water) with a useful reference in future policy-making. Statistics indicate that in 2007 Taipei County had a population of 3,798,015. Tap water was supplied to 3,691,998 people so the water supply coverage rate was 97.21%. The water needs of 29 townships and cities in Taipei County are met by ten tap-water systems overseen by Taiwan Water's 1st Branch, 2nd Branch and 12th Branch as well as the Taipei Water Department. The Taipei water supply system and the Bansin water supply system are the most important systems and together account for 87.13% of total system capacity. Another study indicated that in 2007, Taipei County's total water allocation was 759,604,162 cubic meters. Total volume of water sold was 517,282,357 cubic meters so the water supply system had an efficiency of 68.10%. The water supply coverage was linked to the level of urbanization in local districts. The higher the level of urbanization meant a higher rate of water supply coverage. In 2007, the average water allocation per person in Taipei County was 206 cubic meters per year (approximately 564 liters per day) and average volume of water sold per person was 140 cubic meters per year (approximately 384 liters per day). This was higher than the target of 250 liters per day set by the national government. Up to 242,321,804 cubic meters of water were also unaccounted for in Taipei County in 2007, or around 31.90% of the total water allocation. This includes government water use, firefighting water, water meter error, pipeline leakage and other factors (e.g. pipeline cleaning, water theft). The main cause was pipeline leakage with 240 million cubic meters of water lost. To put this into perspective, the total capacity of the Shihmen Reservoir that year was 210 million cubic meters. If each kiloliter of water costs on average 10 NTD, Taipei County alone cost the national treasury 2.4 Billion NTD.