Interaction between groundwater and trees in an arid site: Potential impacts of climate variation and groundwater abstraction on trees

Yin, L. Z. et al., 2015. Journal of Hydrology

Original research (primary data)
View External Publication Link

Abstract

The understanding of the interaction between groundwater and trees is vital for sustainable groundwater use and maintenance of a healthy ecosystem in arid regions. The short- and long-term groundwater contribution to tree water use was investigated using the HYDRUS-1D model and stable isotopes. For the short-term simulation, the ratio between the actual transpiration (Ta) and potential transpiration (Tp) approached almost ~1.0 due to the constant groundwater uptake. The results from the short-term simulation indicated that the groundwater contribution to tree water use ranged between 53% and 56% in the dry season (May-June) and 16-19% in the wet period (August-September). Isotopic analysis indicated that groundwater contributed to 45% of plant water use in the dry season, decreasing to 4-12% during the wet period. Because of canopy interception and transpiration, groundwater recharge only occurred after heavy rainfall and accounted for 3-8% of the total heavy rainfall. For the long-term simulation, Ta/Tp ranged between 0.91 and 1.00 except in 2007 (0.78), when the water table declined because of groundwater abstraction. In the scenario simulation for deep water table conditions caused by anthropogenic activities, Ta/Tp ranged between 0.09 and 0.40 (mean=0.22) that is significantly lower than the values in the natural conditions. In conclusion, vegetation restoration in arid zones should be cautious as over-planting of trees will decrease the groundwater recharge and potentially cause a rapid drop in water table levels, which in turn may result in the death of planted trees. Trees adapt to arid regions by adopting root patterns that allow soil water uptake by shallow roots and groundwater use by deep roots, thus climatic variation itself may not bring severe negative impact on trees. However, anthropogenic activities, such as groundwater abstraction, will result in significant water table decline that will reduce actual transpiration of trees significantly according to the results from the scenario simulation.

Case studies

Basic information

  • Case ID: INT-218-1
  • Intervention type: Created habitats
  • Intervention description:

    This is an experimental field study to measure the impact of planted willows on water availability (groundwater table). This study is to inform afforestation policy which has/is being used in northern china to address desertification, and erosion. Rainfall/climatic variability is an issue in this region. “The dominated tree in the site is willow (S. matsudana) with a few populous trees. The total number of willow trees are 107 and they were planted in rows in the 1970s (Yin et al., 2014), and the distance between rows is about 5 m and the distance between trees in a row is 4 and 6 m” “The study focuses on groundwater contribution to tree water use, groundwater recharge reduction due to tree canopy interception and the use of soil water, and the impact of water table changes caused by climatic variation and anthropogenic activities on tree water use”

  • Landscape/sea scape ecosystem management: No
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Reduced water availability  Negative HYDRUS-1D (Šimunek et al., 2013) was selected to simulate the interaction between groundwater and plants They compare actual observed transpiration with potential transpiration. They also look at groundwater recharge potentail
  • Approach implemented in the field: Yes
  • Specific location:

    eco-hydrological experimental site near Yulin, Shaanxi province, NW China

  • Country: China
  • Habitat/Biome type: Created forest |
  • Issue specific term: Not applicable

Evidence

  • Notes on intervention effectivness: The intervention is ineffective because the trees use groundwater during the dry and wet season (in comparison with ‘natural conditions’), yet the canopy intercepts rainfall and prevents groundwater recharge. Therefore “For the long-term simulation, Ta /Tp ranged between 0.91 and 1.00 except in 2007 (0.78), when the water table declined because of groundwater abstraction. In the scenario simulation for deep water table conditions caused by anthropogenic activities, Ta/Tp ranged between 0.09 and 0.40 (mean = 0.22) that is significantly lower than the values in the natural conditions. In conclusion, vegetation restoration in arid zones should be cautious as over-planting of trees will decrease the groundwater recharge and potentially cause a rapid drop in water table levels, which in turn may result in the death of planted tree NOTE this is a modeling study, but not a scenario modeling study – they use a model to simulate interaction between groundwater and plants
  • Is the assessment original?: Yes
  • Broadtype of intervention considered: Not applicable
  • Compare effectivness?: No
  • Compared to the non-NBS approach: Not applicable
  • Report greenhouse gas mitigation?: No
  • Impacts on GHG: Not applicable
  • Assess outcomes of the intervention on natural ecosystems: No
  • Impacts for the ecosystem: Not reported
  • Ecosystem measures:
  • Assess outcomes of the intervention on people: No
  • Impacts for people: Not reported
  • People measures:
  • Considers economic costs: No
  • Economic appraisal conducted: No
  • Economic appraisal described:
  • Economic costs of alternative considered: No
  • Compared to an alternative: Not reported

Evaluation methodology

  • Type of data: Quantitative
  • Is it experimental: No
  • Experimental evalution done: Not applicable
  • Non-experimental evalution done: Empirical case study
  • Study is systematic: