李小雁
论文题目：干旱半干旱过渡带雨水集流试验与微型生态集雨模式
作者简介：李小雁，男，1970年12月出生，1997年09月师从于中国科学院寒区旱区环境与工程研究所高前兆教授，于2000年08月获博士学位。
摘 要
干旱半干旱过渡带是生态环境变化的敏感和脆弱地带，气候的波动性和人口压力是生态脆弱的根本原因，干旱和半干旱区交界线在丰枯年份的空间摆动幅度最大达110-130 km。水资源短缺是制约该区经济发展和生态环境改善的主要因素之一，有限的降水资源是生活和农业生产的主要水源，也是可以通过人为措施开发利用的水源。雨水集流是在半干旱区开劈水源，促进生态环境改善与建立新的农业生态系统的一条基本途径。
本论文以干旱半干旱区过渡带作为研究区，通过在中科院寒区旱区环境与工程研究所皋兰生态农业试验站1998-1999年雨水集流实验，结合面上调查，对雨水集流面的产流特征和集水效率、水质和集水利用进行了系统研究，并为脆弱区生态环境建设提出小流域微型生态雨水集流模式。
雨水集流实验研究表明：（1）增加雨水集流系统集水面产流量的基本途径是改变表层土壤结构和植被盖度，增大土质集流区面积和采用人工处理材料的集水面。实验中不同人工集流面的年平均集水效率从大到小为：油毡>沥青>塑料+大砾石>塑料+小砾石>塑料>混凝土>粘土夯实>清除杂草自然面>三合土夯实>自然黄土坡面。（2）集水区的核心问题是降低集水面的降水损失（截留、填洼和入渗）和提高集水效率。前期土壤含水量对土质集水面临界产流降水量的影响为2.5-3.0mm，自然黄土坡面的临界产流降雨量在6-8.5mm之间。平均状态下，塑料膜、油毡、沥青和混凝土处理集水面的临界产流降雨量为0.1-1.5mm，它的产流过程受降雨量和降雨强度的影响小。（3）集雨窖贮易受细菌感染,
对灌溉用水影响不大,但需采取保护和过滤储存才能作为饮用水源（4）雨水集流补灌与农田沟垄微型集雨结合,并配合覆盖蓄水保水措施,能有效地提高降雨的利用效率。田间沟垄微型集雨结合覆盖雨水高效利用技术有效地利用了膜垄的集水和沟覆盖的蓄水保墒功能，改变了降雨的时空分布，使降雨集中富集在种植沟中，显著地提高了降水的利用效率，特别是小雨的利用率。研究结果表明：土垄的平均集水效率为7%，而垄上覆膜后集水效率为87%，膜垄能产生径流的最小降雨量为0.8
mm。田间沟垄微型集雨结合覆盖技术能提高土壤贮水量，增加玉米的产量。垄上覆膜结合沟覆盖处理玉米产量比平地增加2339-5297 Kg hm-2
（44-143%）, 水分利用效率基本都在2 Kg m-3以上。砾石覆盖具有保水保墒，减少径流，增加入渗和提高地温的作用。
基于我国半干旱区现有的经济和生态条件，自然集水面、粘土夯实集水面以及塑料集水面比较经济实用，易于推广。水泥硬化集水面造价较高，应与庭院和道路建设结合。发展庭院经济应优先考虑已有的硬化集水面（如庭院和路面），在充分利用以上集流面的基础上根据不同的目的有选择地进行。根据半干旱区降雨集中分布的特点，建议利用简单临时性的移动塑料集水面收集雨水以供大田作物缺水期补灌。集流水的高效利用方向是将雨水集流和设施农业结合起来，并考虑采用固定集水面。黄土高原生态环境建设要以小流域为单元，把退耕还林生态环境建设与雨水集流结合起来建立微型生态雨水集流系统，³25°自然黄山陡坡以封育为主作为保护水源带，缓坡地以微型集雨为主退耕还林，基本农田要通过各种农业节水措施提高粮食生产能力，并充分利用集雨水发展村庄和庭院发展经济。
关键词：雨水集流
微型生态模式 干旱半干旱区过渡带
Experimental Study on Rainfall Harvesting and Microcatchment Model
for Ecosystem Construction in the Transitional Zone between Semiarid and Arid
Region
Abstract
Transitional zone between the semiarid and arid regions, with a mean
annual rainfall of 250-350 mm, is a climatically sensitive and ecologically
fragile belt. This zone lies in the Monsoon Edge Area in the northern China,
and also is an agriculture and animal husbandry zone. The highly fluctuation of
the climate and population pressure mainly led to the vulnerability of the
regional ecology. The boundary line between arid and semiarid region shift in
the space at a maximum distance of 110-130 km during the extreme dry and wet
year. Water is the key limiting factor for the environmental construction and
agriculture production. Rainfall is the major water resource, and poorly
distributed in time and space. Rainfall harvesting and water saving system
would be an alternative for the improvement of the environment and the
establishment of agricultural ecosystem.
The paper, with
this fragile belt as an interesting study area, was based on the experimental
study on in-situ rainfall harvesting and field investigation. The experiment
was conducted at the Gaolan Research Station of Ecology and Agriculture, Cold
and Arid Regions Environmental and Engineering Research Institute, Chinese
Academy of Sciences., in 1998-1999. The paper was designed to explore runoff
characteristics for various artificial catchments and evaluate the catchments
based on the runoff efficiency, analyze water quality of harvested water from
cistern and catchments, and investigate the effect of on-field rainfall
harvesting and mulching combination on crop production. Based on the above
studies, a microcatchment model for ecosystem
construction was proposed to rehabilitate the
environment of the Loess Plateau.
The main results of the experiments are listed as follows: (1) More
water would be collected from catchments by means of the change of surface soil
structure and the management of vegetation cover, or by increase of natural
catchment area and use artificial catchments. Asphalt sheeting catchment has
the highest runoff efficiencie in the experiment, followed by asphalt spraying,
plastic film covered by lager gravel, plastic film covered by smaller gravel, plastic film, concrete,
compacted clay soil, clear loess slope and natural loess slope catchments. (2)
The purpose of the management of the catchment is to decrease rainfall loss due
to vegetation interception and infiltration. Runoff from natural loess slope
occurred as infiltration-excess process, and it was mainly dependent upon the
rainfall intensity, rain type and antecedent soil moisture. The minimum
runoff-producing rainfall of the natural loess slope is 6-8.5 mm, antecedent
soil moisture decreased the threshold rainfall by 2.5-3.0 mm. The amount of the
rainfall and rain intensity had little effect on the water yield from plastic
film, asphalt felt, and concrete treated catchments, which had a threshold
rainfall of 0.1-1.5 mm. (3) Many water-harvesting systems have no filters
before runoff entering cisterns except silt trap in the Loess Plateau. Usually,
these systems were poorly maintained and prone to fecal contamination. High
content of coliforms was detected in water samples from 7-month storage cellar,
so the rainwater catchment should be often cleaned and some simple filters are
needed in most cases if the water is for human consumption. There is no
difference in water quality from concrete and traditional red clay treated
water cellar, which all can be used to store water for drinking. None of the
surface treatments and storage types appears to affect plant production. (4)
Incorporation of ex-situ supplemental irrigation and in-situ rainfall
harvesting with mulching can better utilize small rainfall events and store
water near the plant roots, it can significantly increase rain use efficiency.
The plastic-covered ridge and furrow rainfall harvesting system combined with
mulches was built by shaping the soil surface with alternate ridges and furrows
along the contour. The plastic-covered ridges served as a rainfall harvesting
zone and furrows as a planting zone. Some materials were also used to mulch the
furrows to increase the effectiveness of the harvested water. This system can
make better utilization of light rain by harvesting rainwater through the
plastic-covered ridge. Plastic-covered ridge had an average runoff efficiency
(runoff / rainfall) of 87% as compared to 7% for bare ridge, and it could
generate runoff at a threshold value of
0.8±0.2 mm rainfall. The
field experiment (using corn as an indicator crop) showed that grain yields in
the system with mulches in 1998 and 1999 were significantly higher than the
controls, with an increase of 4010-5297 kg ha-1 (108-143%). In most
treatments, the water use efficiencies (WUE) were in excess of 2.0 kg m-3.
Gravel mulch can change the hydrological process and improves soil productivity，which is effective in
reducing evaporation and runoff, improving infiltration and soil temperature.
Based on the
current economic and ecological conditions, natural loess slope, compacted clay
soil and plastic film treated catchments are easy to be spread due to low cost,
easy replication and high adaptability. The cost of concrete catchment is high,
and it should be combined with yard and road construction for multi-purpose
use. Priority should be given to rooftop, yard and road pavement catchments for
domestic use and yard economy, then the selection of the optimal catchments
depends on the different purposes. Temporarily moveable plastic film catchment
can be recommended to use in rainy period in the field or yard for storing
rainwater in the cistern for supplementary irrigation. The trend of high
efficient use of harvested water is to combine the water harvesting with
installation agriculture, and the high level artificial catchments can be used.
The ecological environment construction is very important in the loess Plateau.
The Microcatchment Model for Ecosystem Construction, with small
watershed as a unit, is characterized by incorporation of rainfall harvesting
with reversion of tilled land to woodland and grassland. ³25° slope is protected as water
source zone by prevent human and livestock interference, Tree and grass can be
planted in the gentle slope by means of microcatchment water harvesting
techniques. Also the natural slope can be treated as catchment for collecting
runoff into the cistern for supplemental irrigation in the farmland zone, which
is the main part of the system for supply food to farmer by various
water-saving agriculture techniques. The village and yard is the center of
human activity, which can be regarded as an economic zone by using harvested
water to develop greenhouse and stock raising.
Keywords: Rainfall
harvesting, microcatchment model, transitional zone,
semiarid and arid region
