建筑雨水利用指标受估算时间分辨率和边界条件的影响

Influence of estimation temporal resolution and boundary conditions on indicators for assessing architectural rainwater harvesting

自来水替代率和年径流总量控制率是评价建筑雨水利用效果的两个主要考核指标,在设计实践中常通过月均值水量平衡计算得到。提出了一种逐日水量平衡算法,基于含有30年的气象数据的案例进行了比较研究。结果表明,月均值法和日值法分别计算得到的自来水替代率相差了40.5个百分点、年径流总量控制率相差了17.4个百分点,原因在于月均值法不考虑降雨和需水在月内分布的不均匀性。对于以日间水量调度为目标的建筑雨水利用来说,宜采用逐日水量平衡进行具体分析。边界条件(即降雨量和需水量)影响建筑雨水利用效果。以用地组合代表不同的绿化和地面浇洒需水情景,在降雨量少的地方,同一用地组合得到的自来水替代率更低,但年径流总量控制率更高;在同一气候条件下,11种用地组合中有3种可达两个指标的考核基本要求,但都达不到满分要求,若要达到需增加其他雨水回用需求。

Substitution ratio of tap water and volume capture ratio of annual rainfall are two major indicators for evaluating the effects of rainwater harvesting.In current design phase,they are often calculated by monthly water balance analysis.This study proposes a method of daily water balance and then compared the two methods thorough case study with 30 years of meteorological data.The results showed that the difference between substitution ratios of tap water that were calculated by monthly water balance and daily water balance was 40.5%,and the difference between volume capture ratios of annual rainfall was 17.4%.The reason was that the monthly balance did not take into account the uneven distribution of rainfall and water demand between days.It is more accurate to use daily water balance analysis to assess building rainwater harvesting that aims at regulating water between days.Boundary conditions(rainfall and water demand)also have a great influence on the calculation results.Land use combinations represented different water demand scenarios of vegetation and ground watering.The same land combination reached lower substitution ratio of tap water but higher volume capture ratio of annual rainfall at the site with low rainfall.Under the same climate condition,3 of the 11 land use combinations could meet the basic requirements of the two indicators,but none of them could achieve full marks which needed other means of rainwater reuse in addition to vegetation and ground watering.