Increase In Annual Streamflow Research Articles

Catchment hydrological responses to forest harvest amount and spatial pattern

Forest harvest effects on streamflow generation have been well described experimentally, but a clear understanding of process‐level hydrological controls can be difficult to ascertain from data alone. We apply a new model, Visualizing Ecosystems for Land Management Assessments (VELMA), to elucidate how hillslope and catchment‐scale processes control stream discharge in a small Pacific Northwest catchment. VELMA is a spatially distributed ecohydrology model that links hydrological and biogeochemical processes within watersheds. The study site is WS10 of the H.J. Andrews LTER, a 10 ha forested catchment clearcut in 1975. Simulated and observed daily streamflow are in good agreement for both the pre‐ (1969–1974) and postharvest (1975–2008) periods (Nash‐Sutcliffe efficiency = 0.807 and 0.819, respectively). One hundred scenarios, where harvest amounts ranged from 2% to 100% were conducted. Results show that (1) for the case of a 100% clearcut, stream discharge initially increased by ∼29% or 345 mm but returned to preclearcut levels within 50 years, and (2) annual streamflow increased at a near linear rate of 3.5 mm year−1 for each percent of catchment harvested, irrespective of location. Thereafter, to assess the impact of harvest location on stream discharge, 20 harvest scenarios were simulated, where harvest amount was fixed at 20% but harvest location varied. Results show that the streamflow response is strongly sensitive to harvest distance from the stream channel. Specifically, a 20% clearcut area near the catchment divide resulted in an average annual streamflow increase of 53 mm, whereas a 20% clearcut near the stream resulted in an average annual streamflow increase of 92 mm.

기후변동에 대한 한국 하천유량의 탄력성

We investigated the sensitivity of Korean streamflows to climate variation. Historical dam inflows and climate data for eight multi-purpose dam sites were collected and examined to determine key factors affecting streamflow change. The results show that annual streamflow primarily responds to change in precipitation rather than temperature. However, the combination of less precipitation and high temperature induces a more serious decrease in streamflow than does similar precipitation and with low temperature. This result indicates that Korean water resources could be more vulnerable to drought due to increasing temperature caused by global warming. To estimate spatial differences in climate sensitivity, we also calculated climate elasticity for 109 mid-size watersheds using streamflow simulated by the Precipitation Runoff Modeling System (PRMS). Climate elasticity ranges over 1.5~1.9, indicating that a +20% increase in annual precipitation leads to a +30~+38% increase in annual streamflow.

Modelling Sensitivity of Stream flow to Climate Change in the Brahmani River Basin

It is widely accepted that increasing concentration of greenhouse gases in the atmosphere is causing climate change, which may alter the hydrologic cycle and regional water availability. Hydrological modelling to assess the sensitivity of stream flow in the Brahmani basin to different hypothetical climate change scenarios indicated significant changes in mean monthly stream flow. Simulation results indicated 76% increase in annual stream flow with a 30% increase in rainfall and no change in temperature, and a maximum decrease of 33% in annual stream flow with 4°C increase in temperature and 10% decrease in rainfall. Rainfall changes had a greater effect on seasonal as well as annual changes in stream flow than the changes in temperature.

Hydrologic response to extreme warm and cold summers in the McMurdo Dry Valleys, East Antarctica

AbstractThe meteorological characteristics and hydrological response of an extreme warm, and cold summer in the McMurdo Dry Valleys are compared. The driver behind the warmer summer conditions was the occurrence of down-valley winds, which were not present during the colder summer. Occurrence of the summer down-valley winds coincided with lower than typical mean sea level pressure in the Ross Sea region. There was no significant difference in the amount of solar radiation received during the two summers. Compared to the cold summer, glaciological and hydrological response to the warm summer in Taylor Valley included significant glacier mass loss, and 3- to nearly 6000-fold increase in annual streamflow. Lake levels decreased slightly during the cold summer, and increased between 0.54 and 1.01 m during the warm summer, effectively erasing the prior 14 years of lake level lowering in a period of three months. Lake level rise during the warm summer was shown to be strongly associated with and increase in degree days above freezing at higher elevations. We suggest that strong summer down-valley winds may have been responsible for the generation of large glacial lakes during the Last Glacial Maximum when ice core records recorded annual temperatures significantly colder than present.

Changes in water yield after a sequence of perturbations and forest management practices in an Eucalyptus globulus Labill. watershed in Northern Spain

An experimental study to assess the effect of the sequence wildfire–clearfelling–coppice sprout selection–foliar damage caused by a defoliating beetle ( Gonipterus scutellatus Gill.) on seasonal water yield in an Eucalyptus globulus Labill. watershed was carried out in Galicia (NW Spain) from 1987 to 2005. The effect on water yield of a sequence as described in this investigation had not been evaluated till now. A summer wildfire in 1989 caused a mean increase in annual streamflow of 68%, compared with the expected value, during the first three post-fire years. After a clearfelling in 1992 a mean increase of 73% in the annual streamwater was measured for the three following years. A mean increase of 47% in streamflow was observed in the three years after coppice sprout selection in 1995. No effect in streamflow was detected the fourth year after this forestry operation. Finally, a G. scutellatus pest attack resulted in a significant average increase in annual streamwater of 22% from 1999–2000 to 2004–2005. The seasonal deviations (observed minus predicted values) in streamwater during the study period were significantly correlated with precipitation and its seasonality that explained 70% of variation in water yield deviations. Most of significant deviations were measured in autumn and winter. In no case was an increase in water availability observed during summer. No evidence of cumulative effect of those successive perturbations was found. The results presented here could help to evaluate the hydrological consequences of current intensive forest management and frequent perturbations that are affecting E. globulus stands in NW Spain. They might also be used by forest managers to understand the relationship between forest cover and water yield in the context of climate change and reduced rainfall.

The water balance of the Susquehanna River Basin and its response to climate change

Historical precipitation, temperature and streamflow data for the Susquehanna River Basin (SRB) are analyzed with the objective of developing simple statistical and water balance models of streamflow at the watershed's outlet. Annual streamflow is highly correlated with annual precipitation (r2=0.895) and, on a percent basis, changes in annual streamflow (Q̄) are about two times greater than changes in annual precipitation (P̄). Variations in P̄−Q̄, interpreted as annual evapotranspiration, are much smaller than variations in P̄ and Q̄, and are weakly positively correlated with annual mean temperature in accordance with potential evapotranspiration formulae. Streamflow is monotonically related to diagnosed storage of water in the SRB from April through November. Deviations from this trend during winter are interpreted as changes in snowpack, and are in general agreement with climatological snow water equivalent estimates for the basin. A simple, spatially-lumped water balance model of the SRB is developed and shown to capture 99% of the mean annual cycle and 75% of the monthly streamflow from 1900 to 1987. Two “downscaled” predictions of precipitation and one of temperature for a doubling of atmospheric CO2 are used as inputs to the statistical and water balance models of the SRB. The result is an annual streamflow increase of 24±13% (11.8±6.7cm).

Changes in streamflow in an herbicide‐treated Pinyon‐Juniper Watershed in Arizona

A 147‐ha pinyon‐juniper watershed in north‐central Arizona was sprayed with a herbicide mixture to kill all overstory vegetation. After 8 years of postherbicide evaluation, the dead trees were removed. The herbicide treatment induced an increase in annual streamflow of about 157%. There is an indication that after the dead trees were removed, streamflow was reduced to near‐pretreatment levels.