Separating the effects of changes in land management and climatic conditions on long-term streamflow trends analyzed for a small catchment in the Loess Plateau region, NW China

Zhang, L. L. P. et al., 2014. Hydrological Processes

Original research (primary data)
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Abstract

As an integrated result of many driving factors, significant declines in streamflow were observed in many rivers of the Loess Plateau (NW China). This can aggravate the inherent severe water shortages and threatens the regional development. Therefore, it is urgent to develop adaptive measures to regulate the water yield to ensure water security. A key step for successful implementation of such measures is to separate the response of water yield to the main driving factors of land management and climate change. In this study, the variation of annual streamflow, precipitation, potential evapotranspiration, and climatic water balance in a small catchment in the Loess Plateau (near Pingliang, Gansu province) was examined for over five decades, although the relative contribution of changes in land management and climate on the streamflow reduction were estimated. A statistically significant decreasing trend of -1.14mm y(-1) in annual streamflow was detected. Furthermore, an abrupt streamflow reduction because of construction of terraces and check-dams was identified around 1980. Remarkably, 74% of the total reduction in mean annual streamflow can be attributed to the soil conservation measures. Based on a literature review across the Loess Plateau, we found that the impact of changes in land management and climate on annual streamflow diminished with increasing catchment size. This means that there is a dependency on catchment size for the hydrological response to environmental change. This indicates that at least at the local scale well-considered land management may help ensure the water security at the Loess Plateau.

Case studies

Basic information

  • Case ID: INT-206-2
  • Intervention type: Created habitats
  • Intervention description:

    large-scale vegetation restoration e.g. afforestation...woodland and grassland have been mainly established on sloped sites. Although the afforestation and grassland establishment occurred under the same intervention they were spatially distributed and this study provides results for both separately. Therefore it was coded as two interventions.

  • Landscape/sea scape ecosystem management: Yes
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Reduced water availability  Negative "Estimated annual runoff coefficient of various soil conservation measures implemented" - i.e. the contribution of the measure to the level of streamflow
  • Approach implemented in the field: Yes
  • Specific location:

    A representative small watershed on the semi-humid part of Loess Plateau in NW China, Zhifanggou (ZFG), was chosen for this study. It is located in the rural surroundings of Pingliang City (35 260 - 35 330N and 106 370 - 106 420E) of Gansu Province (Figure 1), with a drainage area of 19 km2 and an elevation range of 1365 - 2100 m asl. ZFG is a branch of the Jinghe River, which is the second largest tributary of Yellow River in its middle reaches.

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

Evidence

  • Notes on intervention effectivness: Collect streamflow data over time as well as landuse data (assume that forests on sloped lands are from the intervention) then perform multivariate statistical analysis to determine contribution of each soil conservation practice (including afforestation/grassland creation, dams, terraces etc.) (they also factor out the effects of climate) Although the afforestation and grassland establishment occurred under the same intervention they were spatially distributed and this study provides results for both separately. Therefore it was coded as two interventions. AC & BT 3.20.2020 - The aim of the study is to make a comparison of the different interventions in terms of their effects on streamflow nbs was coded as 'more effective' because really it was just 'less bad', in comparison. Sloped grassland and farmland contributed more to the generation of streamflow than slope forestland. They attribute the difference in the grassland and forest to fact that the effect of different types of vegetation reduce on evapotranspiration and thus water yield differs. Over the landscape, afforested slopes reduce water yield less than check dams (which retain water), but they both reduce water yield, although forests cover has less of a negative effect. it’s important to note that for agriculture, the checkdams and slope farmland actually promote water retention thereby promoting crop growth. Therefore, there are spatial trade-offs in relation to impacts on water availability; the fact that the water availability issue here is scale dependent should be specified
  • Is the assessment original?: Yes
  • Broadtype of intervention considered: Another NbS plus other non-NbS approach(s)
  • Compare effectivness?: Yes
  • Compared to the non-NBS approach: More effective
  • 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:

Basic information

  • Case ID: INT-206-1
  • Intervention type: Created habitats
  • Intervention description:

    large-scale vegetation restoration e.g. afforestation...woodland and grassland have been mainly established on sloped sites Although the afforestation and grassland establishment occurred under the same intervention they were spatially distributed and this study provides results for both separately. Therefore it was coded as two interventions.

  • Landscape/sea scape ecosystem management: Yes
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Reduced water availability  Negative "Estimated annual runoff coefficient of various soil conservation measures implemented" - i.e. the contribution of the measure to the level of streamflow
  • Approach implemented in the field: Yes
  • Specific location:

    A representative small watershed on the semi-humid part of Loess Plateau in NW China, Zhifanggou (ZFG), was chosen for this study. It is located in the rural surroundings of Pingliang City (35 260 - 35 330N and 106 370 - 106 420E) of Gansu Province (Figure 1), with a drainage area of 19 km2 and an elevation range of 1365 - 2100 m asl. ZFG is a branch of the Jinghe River, which is the second largest tributary of Yellow River in its middle reaches.

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

Evidence

  • Notes on intervention effectivness: Collect streamflow data over time as well as landuse data (assume that forests on sloped lands are from the intervention) then perform multivariate statistical analysis to determine contribution of each soil conservation practice (including afforestation/grassland creation, dams, terraces etc.) (they also factor out the effects of climate) Although the afforestation and grassland establishment occurred under the same intervention they were spatially distributed and this study provides results for both separately. Therefore it was coded as two interventions. AC & BT 3.20.2020 - The aim of the study is to make a comparison of the different interventions in terms of their effects on streamflow nbs was coded as 'more effective' because really it was just 'less bad', in comparison. Sloped grassland and farmland contributed more to the generation of streamflow than slope forestland. They attribute the difference in the grassland and forest to fact that the effect of different types of vegetation reduce on evapotranspiration and thus water yield differs. Over the landscape, afforested slopes reduce water yield less than check dams (which retain water), but they both reduce water yield, although forests cover has less of a negative effect. it’s important to note that for agriculture, the checkdams and slope farmland actually promote water retention thereby promoting crop growth. Therefore, there are spatial trade-offs in relation to impacts on water availability; the fact that the water availability issue here is scale dependent should be specified
  • Is the assessment original?: Yes
  • Broadtype of intervention considered: Another NbS plus other non-NbS approach(s)
  • Compare effectivness?: Yes
  • Compared to the non-NBS approach: More effective
  • 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: