•We compare three different schemes for transfer of hydrological model parameters.•Temporal transfer scheme outperforms spatial and spatiotemporal transfer schemes.•Differences between spatial and ...spatiotemporal transfer schemes are negligible.•Temporal gap in calibration and validation periods reduces difference among schemes.
Operational use of hydrological models requires the transfer of calibrated parameters either in time (for streamflow forecasting) or space (for prediction at ungauged catchments) or both. Although the effects of spatial and temporal parameter transfer on catchment streamflow predictions have been well studied individually, a direct comparison of these approaches is much less documented. Here, we compare three different schemes of parameter transfer, viz., temporal, spatial, and spatiotemporal, using a spatially lumped hydrological model called EXP-HYDRO at 294 catchments across the continental United States. Results show that the temporal parameter transfer scheme performs best, with lowest decline in prediction performance (median decline of 4.2%) as measured using the Kling–Gupta efficiency metric. More interestingly, negligible difference in prediction performance is observed between the spatial and spatiotemporal parameter transfer schemes (median decline of 12.4% and 13.9% respectively). We further demonstrate that the superiority of temporal parameter transfer scheme is preserved even when: (1) spatial distance between donor and receiver catchments is reduced, or (2) temporal lag between calibration and validation periods is increased. Nonetheless, increase in the temporal lag between calibration and validation periods reduces the overall performance gap between the three parameter transfer schemes. Results suggest that spatiotemporal transfer of hydrological model parameters has the potential to be a viable option for climate change related hydrological studies, as envisioned in the “trading space for time” framework. However, further research is still needed to explore the relationship between spatial and temporal aspects of catchment hydrological variability.
This study investigates the potential differences between spatial and temporal transferability of the Hydrologiska Byråns Vattenbalansavdelning (HBV) rainfall-runoff model parameters in 576 Iranian ...catchments. Our goal is to determine how parameter transferability is affected by (a) parameter transfer modes (temporal or spatial) and (b) different climate conditions. In the temporal mode, we make decisions in each catchment based on a benchmark baseline that accounts for the seasonality of flows. In the spatial mode, we examine physical similarity and spatial proximity methods. The main conclusions are that: (1) the HBV model struggles to beat the benchmark in lowland catchments; (2) under stationary conditions, rainfall-runoff models have greater temporal transferability than spatial transferability; (3) under non-stationary climate conditions, the number of catchments that perform best in terms of temporal transferability is smaller than in stationary climate conditions; and (4) the rainfall-runoff model has better transferability from drier to wetter conditions.
Agricultural and rural land management practices can have a significant impact on the health of river ecosystems. In this study, our goal was to quantify the extent of land use influence on river ...water quality at two catchments in rural North Wales, Conwy and Clwyd. Stream water samples were collected bi‐weekly from five sampling sites over a three‐month period (September–November 2018) and analyzed in the laboratory to measure six water quality variables, namely, pH, electrical conductivity (EC), phosphorus, nitrate and ammonium concentrations, and bacterial coliform count. We then quantified their relationships with dominant land cover of the contributing catchments using two different land cover classification systems. Significant differences (p < 0.05) were observed across the sampling sites for pH, EC, nitrate and phosphorus concentration, and coliform count. Strong correlations were observed between pH and the proportion of Acid Grassland, and between nitrate levels and the proportion of Improved Grassland in the catchment. The presence of high‐quality agricultural land correlated positively with nitrate and phosphorus concentrations and bacterial coliform count. Conversely, dominance of poor quality agricultural land correlated with lower levels of all the measured water quality indicators. Our results suggest that the proportion of high‐quality agricultural land is a reliable indicator of stream water quality in rural catchments, most likely linked to intensive farming practices.
Research Impact Statement: Our field study at two rural catchments in North Wales UK shows that the proportion of high‐quality agricultural land in a catchment is one of the strongest predictors of its stream water quality.
Straw burning is a significant source of atmospheric pollutants, releasing particulate matter and trace gases. Capturing the characteristics of straw burning and understanding its influencing factors ...are important prerequisites for regulating straw burning. Based on the fire points detected by the Moderate-resolution Imaging Spectroradiometer (MODIS) in Hunan province, China, from 2010 to 2020, this study analyzed the spatiotemporal variations of straw burning and employed Geographically Weighted Regression (GWR) models to investigate the underlying forces driving straw burning. The results show that the spatiotemporal characteristics of straw burning in Hunan Province can be categorized into two distinct periods: 2010 to 2014 and 2015 to 2020. The period from 2010 to 2014 witnessed a rapid increase, while the period from 2015 to 2020 experienced fluctuating decreases. The shift is closely linked to the implementation of the straw burning ban policy in 2015. Spatially, the areas with a high number of fire points are primarily located in the southern regions, especially in the border regions between Chenzhou, Yongzhou, Hengyang, and Shaoyang cities. A significant change was found in the impact of economic development and human activity factors on straw burning before and after 2015. These factors include crop yield, Gross Domestic Product (GDP), and road network development. From the implementation of the straw burning ban policy, increases in GDP and settlement density will have a dampening effect on straw burning in a region. Straw burning locations may shift towards regions with relatively slow economic development. The results could serve as a foundation for decision-making to address the issue of straw burning.
Inland water bodies in China Feng, Shuailong; Liu, Shuguang; Huang, Zhihong ...
Proceedings of the National Academy of Sciences - PNAS,
12/2019, Letnik:
116, Številka:
51
Journal Article
Recenzirano
Odprti dostop
Water bodies (WBs), such as lakes, ponds, and impoundments, provide essential ecosystem services for human society, yet their characteristics and changes over large areas remain elusive. Here we used ...unprecedented data layers derived from all Landsat images available between 1984 and 2015 to understand the overall characteristics and changes of WBs between 2 epochs (i.e., 1984 to 1999 and 2000 to 2015) in China. Results show that the abundance estimate of WBs greater than 1 km² and the total WB surface area were 0.3 to 1.5 times and 0.2 to 0.5 times more than the previous estimates, respectively. The size-abundance and shoreline-area relationships of WBs in China conformed to the classic power scaling law, in contradiction to most previous studies. WB changes with various occurrence probabilities show widespread coexistence of disappearance of existent and emergence of new WBs across China driven primarily by human activities and climate change. Our results highlight the importance of using appropriate long-term satellite data to reveal the true properties and dynamics of WBs over large areas, which is essential for developing scaling theories and understanding the relative impacts of human activities and climate change on water resources in the world.
The objective of this study was to analyze patterns, dynamics and processes of land-use/cover changes in the transboundary Mara River Basin in East Africa. We specifically focused on deforestation ...and expansion of agriculture in the watershed. The intensity analysis approach was used to analyze data from satellite imagery-derived land-use/cover maps. Results indicate that swap change accounted for more than 50% of the overall change, which shows a very dynamic landscape transformation. Transition from closed forest to open forest was found to be a dominant landscape change, as opposed to a random change. Similarly, transition from open forest to small-scale agriculture was also found to be a dominant transition. This suggests a trend (pathway) of deforestation from closed forest to small-scale agriculture, with open forest as a transitional land cover. The observed deforestation may be attributed to continuous encroachment and a series of excisions of the forest reserve. Transition from rangeland to mechanized agriculture was found to be a dominant land-use change, which was attributed to change in land tenure. These findings are crucial for designing strategies and integrated watershed management policies to arrest further deforestation in the forest reserves as well as to sustainably control expansion of agriculture.
Climate change is likely to have a major impact on future hydrological regimes, impacting numerous sectors reliant on surface waters. We use the Soil and Water Assessment Tool (SWAT) to model future ...(2021-2080) streamflow and water quality variables (nitrogen, phosphorus, suspended sediment, and dissolved oxygen), in five catchments in Wales, under a worst-case scenario of future greenhouse gas concentrations (Representative Concentration Pathway 8.5). Results show a decline in annual average flows (−4% to −13%) but larger changes seasonally (spring, up to 41% increase; autumn, up to 52% reduction). The magnitude and frequency of high flow events increasesg in spring (magnitude: Sen's slope range 0.165-0.589, p < .01), with more low flows in autumn (Sen's slope range 0.064-0.090, p < .01). Water quality declines, with higher nitrogen, phosphorus, and sediment concentrations and lower dissolved oxygen levels. The findings have economic and environmental implications for abstractors, as water resources could become more unreliable, seasonal, and polluted.
Abstract
Run-of-river hydropower in the United Kingdom (UK) and Ireland is a small but vital component of renewable electricity generation that enhances grid diversification and resilience, ...contributes to the net-zero emissions targets, and provides local community benefits. Planning approval by environmental regulators for hydropower water abstraction is based on the abstraction licence conditions (ALCs) that dictate when and how much water may be taken from a given stream location. Although ALCs for non-environmentally sensitive rivers vary across England, Wales, Scotland, Northern Ireland, and Ireland, the impacts of these variations on power generation are not fully understood. Here, we investigate how ALC variations across the UK and Ireland have historically impacted water abstraction and power generation and might continue to do so under future climate conditions. Specifically, we apply five distinct ALCs combination sets, as laid out by the five environmental regulators in the region, to historical observed streamflows and future projected flows (modelled for the Representative Concentration Pathway 8.5 scenario using the EXP-HYDRO hydrological model), at 531 hydropower sites across the UK and Ireland. We then calculate the daily water abstraction potential for each hydropower site and the collective power generation potential separately for Great Britain (GB) and the Island of Ireland (IoI). Our results show that the ALCs that permit greater use of lower flows allow for more power generation than those that enable abstraction during high flow conditions. The most optimal combination of ALCs for power generation, when compared to those currently in use, increases future generation potential by 30.4% for GB and 24.4% for the IoI, while maintaining environmental protection as per the Welsh guidelines. Our results suggest that ALC policy and regulatory reforms are needed to provide optimal use of future streamflows for hydropower generation while ensuring protection for the environment is maintained.
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