Multi-temporal runoff-sediment discharge relationships

To understand the runoff-sediment discharge relationship , this study examined the annual runoff and sediment discharge data obtained from the Tangnaihai hydrometric station. The data were decomposed into multiple time scales through Complete Ensemble Empirical Mode Decomposition with adaptive noise (CEEMDAN). Furthermore, double cumulative curves were plotted and the cointegration theory was employed to analyze the microscopic and macroscopic multi-temporal correlations between the runoff and the sediment discharge and their detailed evolution.

The Effects of Rainfall Patterns on Runoff, Sediment, and Nutrients Under Various Artificial Rainfall Experiments

Assessing the effects of rainfall patterns on runoff, sediment, nutrients under variation of rainfall pattern are significant in the quantification of sediment transported by overland flow. Previous experimental and field works studied that sediment transport is influenced by hydraulic properties of flow, physical properties of soil and surface characteristics. This study aims at determining the effect of rainfall patterns on surface runoff, sediment loss and nutrient loss. Experiments were carried out using four rainfall patterns, namely Pattern A (uniform-type: 8-8-8 l/min), Pattern B (increasing-type: 7-8-9 l/min), Pattern C (increasing-decreasing-type: 7-9-8 l/min) and Pattern D (decreasing-type: 9-8-7 l/min) with the changes of intensity every 30 minutes that gives total rainfall duration of 90 minutes for each pattern. The simulation was performed in three repetitions. The average total runoff produced was 668.65, 701.40, 699.10, and 722.63 liters, for rainfall patterns A, B, C, and D, respectively. The trend of runoff generated was influenced by the rainfall patterns, Pattern D generated the highest amount of runoff meanwhile Pattern A generated the lowest. For total suspended sediment concentrations, the mean value among every three repetitions of rainfall pattern resulted as 14,518.88, 13,732.73, 8,011.71 and 19,918.50 mg/l for patterns A, B, C, and D, respectively Pattern D contributed to the highest amount of sediment accumulated whereby Pattern C generated the lowest sediment despite the trend showed a different approach than the other 3 patterns. In nutrient concentrations, the determined total losses for ammonia nitrogen were 3.986, 2.891, 3.504, and 4.601g; nitrate nitrogen were 3.934, 2.665, 4.008, and 3.259g; phosphorus were 1.346, 0.222, 0.207, and 0.679g, for patterns A, B, C, and D, respectively. In general, rainfall pattern does have a significant impact on the trend of nutrient losses, where the trend shows that higher concentrations at the start and eventually lowered through the end, but Pattern D as compared to other patterns resulted in a more severe nutrient loss. For the affected area of the soil movement process, the calculated means of the affected area are 79.60, 68.70, 72.43, and 64.97% for patterns A, B, C, and D respectively. The lowest mean of the affected area is contributed by Pattern D and the highest by Pattern A.

Multi-Disciplinary Assessment of Napier Grass Plantation on Local Energetic, Environmental and Socioeconomic Industries: A Watershed-Scale Study in Southern Thailand

Napier grass is an energy crop that is promising for future power generation. Since Napier grass has never been planted extensively, it is important to understand the impacts of Napier grass plantations on local energetic, environmental, and socioeconomic features. In this study, the soil and water assessment tool (SWAT) model was employed to investigate the impacts of Napier grass plantation on runoff, sediment, and nitrate loads in Songkhla Lake Basin (SLB), southern Thailand. Historical data, collected between 2009 and 2018 from the U-tapao gaging station located in SLB were used to calibrate and validate the model in terms of precipitation, streamflow, and sediment. The simulated precipitation, streamflow, and sediment showed agreement with observed data, with the coefficients of determination being 0.791, 0.900, and 0.997, respectively. Subsequently, the SWAT model was applied to evaluate the impact of land use change from the baseline case to Napier grass plantation cases in abandoned areas with four different nitrogen fertilizer application levels. The results revealed that planting Napier grass decreased the average surface runoff and sediment in the watershed. A multidisciplinary assessment supporting future decision making was conducted using the results obtained from the SWAT model; these showed that Napier grass will provide enhanced benefits to hydrology and water quality when nitrogen fertilizers of 0 and 125 kgN ha−1 were applied. On the other hand, the benefits to the energy supply, farmer’s income, and CO2 reduction were highest when a nitrogen fertilization of 500 kgN ha−1 was applied. Nonetheless, planting Napier grass should be supported since it increases the energy supply and creates jobs while also reducing surface runoff, sediment yield, nitrate load, and CO2 emission.

Spatial and temporal effects of climate change and land use change on runoff, sediment, nitrogen and phosphorus loss in the Haihe River Basin over the past 40 years

Investigating the impacts of climate and land use changes on basin’s hydrological cycle and environment is important to provide scientific evidence to manage the trade-off and synergies among water resource, agricultural production and environment protection. In this study, we quantified the contributions of climate and land-use changes to runoff, sediment, nitrogen and phosphorus losses in the Haihe River basin since the 1980s. The results showed that (1) climate and land-use changes significantly increased evapotranspiration (ET), transport loss (TL), sediment input (SI) and output (SO), and organic nitrogen (ON) and phosphorus production (OP), with ET, SI, and ON affected most. (2) The runoff, sediment and ammonia nitrogen were affected most by climate and land use changes in the Daqing River Basin (217.3 mm), Nanyun River Basin (3917.3 ton) and Chaobai River Basin (87.6 kg/ha), respectively. (3) The impacts of climate and land-use changes had explicit spatial-temporal patterns. In the Daqing River, Yongding River and Nanyun River, the contribution of climate change to runoff and sediment kept increasing and reached 88.6%~98.2% and 63%~77.2%, respectively. In the Ziya River and Chaobai River Basin, the contribution of land use was larger, reaching 88.6%~92.8% and 59.8%~92.7%, respectively. In the Yongding River Basin, Chaobai River Basin, Ziya River Basin and Daqing River Basin, the contribution of land use to nitrogen and phosphorus loss showed an increasing trend in the past 40 years (maximum: 89.7%). By contrast, in Nanyun River and Luanhe River, the contribution of climate change to nitrogen and phosphorus loss increased more obviously (maximum: 92.1%). We quantitatively evaluated the spatial and temporal impacts of climate and land-use changes on runoff, sediment, and nitrogen and phosphorus loss, which are useful to support the optimizations of land and water resources in the River Basin.

Influence of tied-ridge with biochar amendment on runoff, sediment losses, and alfalfa yield in northwestern China

Background Loss of organic matter and mineral nutrients to soil erosion in rain-fed agriculture is a serious problem globally, especially in China’s Loess Plateau. As a result, increasing rainwater usage efficiency by tied-ridge-furrow rainwater harvesting with biochar is expected to improve agricultural productivity. Nonetheless, with limited knowledge on tied-ridge-furrow rainwater harvesting with biochar, small-scale farmers face the challenge of adoption, thus, the rationale for this study. Materials and methods A field experiment was conducted to determine the influence of open-ridging (OR) and tied-ridging (TR) with bio-degradable film on ridges and biochar in furrows on runoff, sediment losses, soil moisture, fodder yield, and water use efficiency (WUE) on sloped land, using flat planting (FP) without ridges and furrows as control, during alfalfa-growing year (2020). Results Runoff in flat planting (30%), open ridging (45%), and tied ridging (52%) were decreased with biochar to the extent where sediment was decreased in flat planting (33%), open ridging (43%), and tied ridging (44%) as well. The mean runoff efficiency was lower in flat planting (31%), open ridging (45%), and tied ridging (50%) in biochar plots compared to no-biochar plots. In biochar and no-biochar plots, soil temperature on ridges of TR was higher than that on OR, which was higher than FP during alfalfa growing season. Soil temperature in furrows during alfalfa growing season in biochar and no-biochar plots were in the order FP > OR > TR. Mean soil water storage for FP, OR, and TR, in biochar plots was higher than in no-biochar plots. This indicates biochar has a beneficial impact on open riding. Total annual net fodder yield (NFY) was significantly (p = 0.00) higher in treatments in the order TR > OR > FP. Tied ridging had a significant effect on actual fodder yield (AFY) in biochar plots, while open ridging significantly affected AFY in no-biochar plots. Annual total mean NFY and AFY increased by 8% and 11% in biochar plots compared to no-biochar plots. In biochar and no-biochar plots, water use efficiency was in the order TR > OR > FP. Conclusively, water use efficiency was significantly higher (p = 0.01) in biochar plots compared to no-biochar plots. Conclusion When crop production is threatened by soil erosion and drought, mulched tied-ridge with biochar is beneficial to crop growth in rain-fed agriculture, according to this research. Smallholder farmers should be trained on applying this technique for water-saving to mitigate runoff, soil erosion, sediment losses, and improve food security in semiarid areas.

Runoff, Sediment and Nutrients Loss from Two Small Watersheds in Eastern Plateau and Hill Region of India

Hydrologic behaviour of many small watersheds around the world are changing mainly due to alterations in land use land cover, and creating new regimes of hydrologic response by driving changes in runoff, sediment and nutrient dynamics. In this study, response of two small watersheds, Plandu and Keribanda, located in eastern plateau and hill region (EPHR) of India was assessed in terms of runoff, sediment and nutrient loss. Daily discharge at the outlets of watersheds was monitored, and water samples were collected at weekly intervals during the monsoon seasons of the years 2015, 2016, and 2017. Water samples were analysed for sediment, Nitrogen (N), Phosphorous (P) and Potassium (K) concentrations. The peak discharge rate from the Plandu and Keribanda watersheds ranged between 5.35 m3 .s−1 to 8.58 m3 .s−1, and 8.41 m3 .s−1 to 11.79 m3 .s−1, respectively. The Plandu watershed yielded 47.4 % higher sediment yields compared to the Keribanda watershed on account of extensive agricultural activities during the monsoon season. The Plandu watershed also recorded higher N (1.17 kg.ha−1.y−1) and P (0.19 kg.ha−1.y−1) losses; however, the K loss (22.92 kg.ha−1.y−1) was higher in the Keribanda watershed. Linear regression models were also developed between rainfall-runoff (R2: 0.86-0.89), runoffsediment yield (R2: 0.82-0.88), N, P, and K loss with runoff volume (R2: 0.82-0.94). The findings of this study would aid in devising informed policies for soil, water and nutrient management strategies at the watershed scale.