北方土石山区坡地生态水文过程及其驱动机制研究

North China is facing the severe water shortage. Taihang mountain area has been acted as the important natural ecological barrier and the significant water recharge area of the North China Plain, while it is still unclear about the water conversion characteristics, driving factors and mechanisms in the typical rock-soil slope in Taihang mountainous area. Water, as the most active factor in the mountain surface system and the limiting factor in ecological restoration, it is of great significance to clarify the eco-hydrological processes of slope. However, the current studies on the eco-hydrological processes of slope in rocky Taihang mountainous area often focuses on the upper soil layer, and there is insufficient consideration on the lower weathered rock layers. In addition, the full answer can’t be got about the question that how does the slope geologic body make the subsurface runoff so common in the mountain area with annual average 560 mm precipitation? In this study, the slope characterized by weathering layer of gneiss beneath a shallow soil layer is taken as the study object, and the following researches will be done by field observation, indoor and outdoor experiments. (1)Clarify the redistribution characteristics of precipitation in slope; (2)Investigate the characteristics of rock-soil interface, fracture and rock mass network; clarify the effect and mechanism of water exchange between fissure and rock mass on the slope hydrology processes; (3)Reveal the eco-hydrological relationship between subsurface runoff and vegetation community; (4)Calculate the interface water flux and seek possible artificial ways to control water movement in groundwater-rock-soil-plant-atmosphere-continuum (GRSPAC). The study is helpful to deeply understand the hydrological cycle process and the mechanisms of water resources formation and transformation in the northern mountain area in China, and is beneficial to provide a scientific reference to improve the water conservation function and rational water use in mountain area.

面对华北严重缺水问题，太行山区作为华北平原的天然生态屏障和重要水源地，其水循环演变规律、影响因素及其驱动机制尚不清楚。水分作为土石山区表层系统中最活跃的因子和生态修复的限制性因素，明确坡地生态水文过程具有重要意义。但是，目前针对土石山区坡地生态水文过程的研究，往往侧重于上部土壤层，对下部风化岩体层考虑不够；另外，究竟是什么样的坡地水文地质体，保证年均降水560mm的太行山区非饱和渗流的普遍、客观存在，目前还无法全面回答。本研究以岩土二元介质坡地为研究对象，通过野外观测与室内外实验相结合的方法，研究坡地降雨再分配特征，探讨岩土界面特征、裂隙网络特征及裂隙-岩块间的水交换特征对坡地水文过程的影响机制，揭示植被群落的生态水文效应，探索地下水-岩体-土壤-植物-大气连续体(GRSPAC)各界面水分通量计算与人工调控的可能途径。该研究有助于深入认识与理解山区水循环过程、水源涵养与水资源形成调控机制。

面对华北地区严重缺水问题，太行山区作为华北平原重要水源地，其水循环演变规律、影响因素及其驱动机制尚不清楚。目前土石山区坡地生态水文过程的研究，侧重上部土壤层，对下部风化岩体层考虑不够。开展土石山区坡地岩土水分运移机制和流域水源涵养特征等相关研究，有助于深入认识与理解山区水循环过程、水源涵养与水资源形成及调控机制。（1）通过野外定位观测与模拟试验，揭示了坡地岩土二元介质定水头积水入渗试验特征，发现岩土分异面特征、裂隙网络特征及裂隙-岩块间的水交换特征是影响岩土二元介质非饱和渗流的主要因素；对不同植被条件下土壤水分动态变化特征研究发现，荆条灌丛是该地区主要耗水物种，在植被生态修复中，应尽量减少荆条的覆盖面积；对低山丘陵区优势植物水分利用来源时空格局研究表明，刺槐与酸枣能够较为稳定的利用深层土壤水分，两者水分利用来源重叠率高达80%以上，而荆条水分利用来源则随季节变化灵活，旱季可同时吸收深层和浅层土壤水分，雨季则以浅层土壤水分为主。（2）通过野外采样与室内分析，以典型河流为研究对象，得出大清河山区流域地表水和地下水水化学类型主要是HCO3-Ca型，雨季前后地表和地下水δD和δ18O均呈现较好的线性相关性，地表和地下水交换频繁，雨季后交换比超过50%。（3）采用遥感数据和模型模拟，以典型流域为研究对象，得出山区流域形状为狭长形，水系为5-7级，河道坡度与产水模数呈显著正相关。进行山区不同土地利用类型水源涵养特征研究发现，降水、蒸散发及其协同作用是影响山区流域水源涵养量空间分异主要因素。基于此，建立了山区不同植被类型生态水文过程和山区碎屑岩土水分运移与转化研究观测体系2套，并提出了多种土石山区生态修复与水源涵养功能提升的技术方法，包括陡峭石质山体雨水外集内蓄系统、利用荆条灌丛提升土石山区水源涵养能力的方法等。该结果可为京津冀山区水源涵养功能提升提供一定的理论依据和技术支撑，对水源涵养功能区建设具有重要的指导意义。