新中国成立后尤其是改革开放以来，小水电在我国得到了快速的发展，但却呈现出“小 而多、小而乱、小而偏”等特点。相比于大水电，小水电的生态影响直到近些年因导致频 繁的河流断流才被人们关注；目前为数不多的关于小水电开发对局地生态系统影响的研究， 得出的结论呈现较大的差异；不同地区对小水电的开发也呈现严格控制与支持鼓励两种截 然不同的态度。究其原因，主要是因对小水电生态影响评价的对象、尺度以及视角的差异 造成的。因此，亟需从系统的视角、更宏观的范围对我国小水电生态影响进行解析与评估。 从生命周期角度来看，小水电开发建设不仅会对当地生态系统产生影响，也会因消耗社会 经济资源对其他尺度生态系统造成影响，而现有的生命周期评价（Life Cycle Assessment， LCA）方法体系缺乏对生态影响的有效度量。鉴于此，本文将投入产出分析方法与能值分 析方法相结合，构建了 Eco-LCA 模型（Ecologically-based LCA model）；选取典型案例， 深入对比分析了我国不同地区、不同模式、不同梯级强度的小水电全生命周期生态影响， 探究不同维度下相对适宜的小水电开发条件，主要研究内容和结论如下：

（1）基于生物物理视角，系统解析了我国小水电的生态影响机理，即对生态系统结 构和功能的改变。首先，小水电的建设运行会改变当地自然生态系统，因大量社会经济资 源投入导致当地系统原有的景观结构被破坏，以及因拦截引流导致水量时空分布变化对河 流生态系统产生干扰。除此之外，小水电对生态系统的改变还包括消耗的社会经济资源在 其上游生产过程中对其他生态系统所产生的改变，即间接影响。小水电建设运行消耗了国 民经济中的社会经济资源，其生态影响就会沿着产业链进行“传递”，这些间接影响会在 社会经济系统不同产业部门、产业阶段中体现出来。因此，需从全生命周期不同阶段完整 地考虑小水电对不同尺度生态系统结构与功能的改变。

（2）从系统生态学出发，基于 2012 年国家经济投入产出表编制了我国 2012 年生态 投入产出数据库，建立 Eco-LCA 模型。通过能值核算国民经济系统的可再生能源、非可再 生资源消耗及其导致的生态系统服务损失，计算出我国 2012 年 139 个国民经济部门的生 态成本强度。该数据库可以用于构建混合 Eco-LCA 模型，开展不同工程项目、尤其是可再 生能源开发项目的生态影响研究，为我国可再生能源开发项目的生态影响系统评估提供新 的方法体系。

（3）采用混合 Eco-LCA 模型，即利用传统能值分析核算小水电建设运行对局地生态 系统的直接干扰、采用 Eco-LCA 模型核算其因消耗社会经济资源产生的对其他尺度生态系 统的间接影响，对不同维度下小水电的生态影响进行核算，主要结果如下：①对比分析我 国三个不同地区（贵州、湖南、西藏）的三个装机容量相似、同为引水式开发的小水电全 生命周期生态影响，结果表明三个水电站的直接影响均占到全生命周期生态影响的 80%左 右；相关指标表明贵州小水电生态影响最小，这主要是因为贵州的小水电水能资源最为丰富，开发单位水能资源所需投入的非可再生资源最少；湖南的小水电水能资源相对稍贫乏， 所需非可再生资源增多，生态影响随之增大；西藏水能资源也很丰富，但因主电网建设落 后，小水电为离网运行，装机容量小，仍需相当规模的水工建筑物，生态影响最大。②针 对不同的水资源利用程度，以贵州省小水电为例，对其生态影响进行敏感性分析，结果表 明即使年发电量降低到 50%的设计发电量，系统的生态影响也要小于其他地区；而一旦过 度开发，挤占了下游河道生态需水，导致河流断流，其生态影响就会急剧增大，甚至高于 其他地区。③对于不同模式的小水电，核算并对比分析了西藏那曲地区三个装机容量相似、 不同开发模式的小水电全生命周期生态影响。结果表明水工建筑结构最简单的引水式水电 站对生态系统的影响最小；混合式和筑坝式水电站因大坝的建设需投入大量非可再生资源， 此外还有淤积在水库中的泥沙投入，增大了对生态系统的压力，其中筑坝式的生态影响最 大。④最后选取湖南省石门县渫水中上游的三级梯级小水电开发案例，首先通过建立系统 动力学模型模拟了梯级水电站来水与发电量的过程，结果表明第一级水电站严重影响了第 二级水电站的电力产出和断流时间，这是因为第一、二级水电站分布过于密集，第二级水 电站累积水头低，发电所需河水流量大。其次采用混合 Eco-LCA 模型，对比 4 种不同开发 强度（第一级、第一级和第二级、第一级和第三级、三级）的小水电生态影响，结果表明 无论是否考虑河流生态系统退化，都以第一级和第二级形成的梯级开发系统环境表现最差。 若不考虑河流生态系统退化，第一级和第三级形成的梯级水电开发系统环境表现最好；若 考虑下游河流生态系统退化，只有第一级水电站时，系统的生态影响最小，但仍因河流生 态系统服务损失的投入，系统能值可持续指标为 0.86，小于 1，呈现不可持续性。可以看 出在保障河流生态需水的前提下，第三级水电站的开发优化了河流水电开发的环境表现， 而第二级水电站的开发增大了对生态环境的干扰，出现河流水电开发的边际效应。

（4）基于以上对比分析结果，对我国不同维度下相对适宜的小水电开发条件进行探 讨。发现在不同模式中，引水式是相对最适宜的开发模式；在不同区域中，贵州是相对最 适宜的开发区域，湖南次之，而西藏的小水电无论哪种开发模式，生态影响都要高于其他 地区，相对最不适宜开发小水电；在不同水资源利用程度中，保障下游河道生态需水是减 缓生态影响的关键；而在不同梯级开发强度中，需要规划适当密度的小水电开发，防止边 际效应的出现。基于此，提出了我国未来小水电开发在优先模式、优先区域选择及不同地 区小水电规划、运行中的适应性管理建议，以优化小水电的生态影响。综合来看，小水电 开发一定是有生态影响的，但应根据开发需求与生态保护的权衡，优化小水电的开发，而 不是一味地严格控制所有小水电开发。

Since the founding of new China, eapecially the reform and opening up, small hydropower (SHP) has experienced rapid development in the whole country. Compared to large hydropower, public did not pay much attention to the ecological impacts of SHP until the frequent drying-up of rivers caused by SHP plants recently. Limited research associated with the ecological impacts of SHP showed very different conclusions. Different provinces also adopt very different attitudes towards SHP development, i.e., to halt or to encourage SHP development. It is caused by the differences of case, scale and perspective of ecological impacts of SHP. In such context, it is imperative to analyze and to evaluate the ecological impacts of SHP systematically. From the perspective of life cycle, the development of SHP plants not noly exert impacts on local ecosystem, but also exert impacts on other ecosystems due to the consumption of economic products. However, the current life cycle assessment (LCA) methodoly lacks the quantification of ecological impacts. Therefore, this thesis develops the Eco-LCA (Ecologically-based LCA) model by combining the emergy analysis and input-output analysis; and compares the life-cycle ecological impacts of SHP plants in different provinces, different schemes and different cascades to explore the relatively suitable conditions in different dimensions. The main conclusions are addressed as follows:

(1) The ecological impacts of SHP plants were analyzed from the biophysical perspective, i.e., the changes in the structure and function of the ecosystem induced by SHP plants. Firstly, the construction and operation of SHP plants changed local ecosystem, which mainly involved two aspects: disturbances of original landscape due to the investment of substantial external resources, and downstream river ecosystem degradation due to impounding and diverting water. Moreover, it also changed other ecosystems due to the consumption of economic products, i.e., the indiect ecological impacts. The construction and operation of SHP plants consumed the economic products from national economy. Thus, the ecological impacts would transmit along the industry chain, which would be demonstrated in different industrial sectors and phases among the socio-economic systems. Therefore, the ecological impacts of SHP plants on different ecosystems should be evaluated from the whole life cycle.

(2) The ecological input-output database was developed based on the latest development of input-output analysis and 2012 economic input-output table of China. Through the emergy accounting of renewable and nonrenewable resources utilized by national economy as well as the ecosystem services losses caused by national ecosystem degradation, the ecological cost intensity (i.e., emergy intensity) of the 139 industry sectors was accounted for. This database can be used to develop hybrid Eco-LCA model to study the ecological impacts of SHP during its whole life cycle, and also can be used to the study of ecological impacts of other projects, such as large hydropower and wind power.

(3) Using the hybrid Eco-LCA model, to be specific, using the traditional process-based emergy analysis to evaluate the on-site ecological impacts induced by SHP, and using the Eco-LCA to evaluate the indirect ecological impacts on other ecosystems due to the consumption of economic products, the life-cycle ecological impacts of SHP plants in different dimensions are evaluated. The main results are as follows: ① the life-cycle ecological impacts of three diversion-scheme SHP plants with similar installed capacities in three different provinces, i.e., Guizhou, Hunan, and Tibet, were evaluated and compared. The results showed that approximately 80% of the life-cycle ecological impacts are derived from the on-site disturbances among all the three case SHP plants. And the case SHP plant in Guizhou Province induced lowest ecological impacts and obtained highest sustainability due to the highest hydroenergy “quality”. Then the case plant in Hunnan Province came second. Though Tibet possesses abundant hydro resources, the case plant was off-grid operation. Due to the low electricity demand of local residents, the plant was installed with a small capacity, whereas sizable civil works were required. Thus, the plant exerted largest ecological impacts. ② As for different utilization level of water resources, the case SHP plant in Guizhou Province was taken as an example. Through the sensitivity analysis of the ecological impacts of SHP plant, the results showed that even if the annual electricity output decreased to 50% of the designed electricity output, its environmental performance is also better than that in other provinces; whereas once the plant occupied the downstream environmental flows and led to the drying-up, the ecological impacts would become serious, even higher than that in other provinces. ③ Regarding the different schemes, the ecological impacts of three SHP plants with similar installed capacity but different schemes in Nagqu, Tibet, were evaluated and compared. The results showed that the diversion-based scheme obtained the best environmental performance and sustainability due to the simple civil works. The hybrid scheme and dam-toe based scheme required substaintial nonrenewable resources due to the construction of dams and the sediment blocked in the reservoir. ④ Finally, taking the three casacade SHP plants on the upper Xie River in Shimen County, Hunan Province as an example, the relationship between the cascade reservoir inlet-outlet flows and electricity output was simulated through the system dynamics model. The results showed that the upstream SHP plant affected the electricity output and drying-up period of downstream plant. Then using the hybrid Eco-LCA model, the ecological impacts of different cascade SHP development intensities (the first, the first+second, the first+third, three plants) were evaluated and compared. The results showed that whether including the river ecosystem degradation or not, the first+second plants exerted largest ecological impacts. If river ecosystem degradation was not included, the first+third plants obtained best environmental performance; if it was included, only the first plant produced smallest ecological impacts, whereas the emergy sustainability index was 0.86, smaller than 1, showing that the system was not sustainable in the long term. It can be seen the construction of the third plant optimized the environmental performance of hydropower development if downstream environmental flows are guaranteed, whereas the construction of the second plant increased the ecological impacts and showed the marginal effect.

(4) Based on the above results, the relatively suitable conditions for SHP development in different dimensions were explored. Among different schemes, the SHP in diversion scheme is the most suitable to be developed. Among different provinces, Guizhou is the most suitable area to develop SHP, and Hunan comes second. Tibet is relatively not suitable to develop SHP since SHP development with any scheme in Tibet could give rise to higher intervention to the ecosystem than for other regions. Among the different water utilization levels, downstream environmental flow is essential to decrease the ecological impacts of SHP plants in provinces such as Guizhou. Among the different cascades of SHP developmet, suitable cascades should be planned to prevent the marginal effect. Finally, the adaptive management suggestions about prior scheme and prior provinces to develop SHP as well as the design and operation in different provinces are recommended to optimize the ecological impacts of SHP. Overall, the SHP development would produce ecological impacts, and the SHP development should be determined by the trade-off between the demand and ecosystem protection instead of forbidding all the SHP development blindly.