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"Water Movements"
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Breaching the peace : the Site C Dam and a valley's stand against big hydro
\"Breaching the Peace tells the story of the ordinary citizens who stood up to the most expensive megaproject in BC history and the government-sanctioned bullying that propelled it forward. Starting in 2013, journalist Sarah Cox travelled to the Peace River Valley to talk to locals about the Site C dam and BC Hydro's claim that the clean energy project was urgently needed. She discovered farmers, First Nations, and scientists caught up in a modern-day David and Goliath battle to save the valley, their farms, and traditional lands from wholesale destruction. Told in frank and moving prose, their stories stand as a much-needed cautionary tale at a time when concerns about global warming have helped justify a renaissance of environmentally irresponsible hydro megaprojects around the world.\"--Provided by publisher.
Book
Growing Season Precipitation Percolates to Groundwater Past Older Water in Storage Across a Temperate Agricultural Catchment
How water is stored within‐ and released from‐the vadose zone controls groundwater recharge, plant water uptake, and the movement of dissolved solutes (nutrients, carbon, pollutants). The goal of this study was to determine the age of water recharging groundwater during the growing season in a temperate agricultural catchment. We measured soil moisture and bulk soil water isotopic compositions (δ18O) twice per month at three locations across a hillslope as well as groundwater and surface water δ18O near the catchment outlet from March through October. We then calibrated ecohydrological models to these data with two competing representations of vadose zone flow: two‐pore domain flow (TPD) and well‐mixed flow (WM). Measurements of moisture δ18O across the upper 40 cm of the soil profile and in surface and groundwater all supported selection of TPD over WM as the more likely representation of vertical water movement through the vadose zone. Calibration of the TPD model resulted in substantially different soil parameter estimates from that of the WM model. The TPD model indicated that growing season percolate to groundwater was composed of water 1–2 weeks old, whereas evapotranspiration (ET) was sourced from prior seasons. In contrast, the WM model suggested that both percolate and ET originated as precipitation from prior months. These results carry significant implications for conceptual and numerical modeling of the fate and transport of nutrients that are surface applied to agricultural fields. Our findings highlight a critical need for improved process representations of soil water transport in hydrological and ecohydrological models.
Journal Article
An experimental and numerical investigation of the mechanism of improving the rainwater retention of green roofs with layered soil
Improving the rainwater retention capacity (RRC) of green roofs has been proposed as an important component of urban stormwater management. In this study, a two-layered soil green roof model was established to enhance RRC compared to each single soil column model. The hydrological process of layered soil green roofs was simulated using the HYDRUS-1D program, with simulation results verified by measured results. The results showed that the RRC of the layered soil was 5% and 1% higher than that of each single substrate under a long-term dry-wet cycle and increased by 15% and 11% per event compared with the single substrates. In addition, higher peak drainage reduction and longer peak drainage delay were observed in the layered soil green roof compared to each single soil. The layered soil slowed the movement of the soil wetting front and increased the maximum water content of the upper soil. The water loss of the layered soil was reduced after rainfall and mainly occurred in the lower layer of the layered soil. These results suggest that the structures of green roofs with an upper layer with higher permeability and a lower layer with lower permeability have better hydrological performance.
Journal Article
Evolution of soil-water states in the vadose zone of a desert soil after an extreme rainfall event and its impact on the ecosystem
Evolution of soil-water movement patterns following rare and extreme rainfall events in arid climates is not well understood, but it has significant effects on water availability for desert plants and on the hydrological cycle at small scale. Here, field data and the Hydrus-1D model were used to simulate the mechanisms of soil water and vapor transport, and the control factors associated with temporal variability in the soil water and temperature were analyzed. The results showed that thermal vapor transport with a no rainfall scenario determined daily variability in water content at the soil surface. During rainfall, isothermal liquid water fluctuated as a result of dry sandy soils and matric potential in the upper soil (0–25 cm), and thermally driven vapor played a key role in soil-water transport at 40–60 cm soil depth. After an extreme rainfall event, thermal vapor flux increased and accounted for 11.8% of total liquid and vapor fluxes in daytime with a steep temperature gradient; this was very effective in improving long-term soil-water content after the rain. The simulated results revealed that thermal water vapor greatly contributed to the soil-water balance in the vadose zone of desert soil. This study provided an alternative approach to describing soil-water movement processes in arid environments, and it increased understanding of the availability of water for a desert plant community.
Journal Article
Using Soil Water Stable Isotopes to Investigate Soil Water Movement in a Water Conservation Forest in Hani Terrace
Water conservation forests significantly contribute to the stability of mountain agricultural ecosystems in Hani Terrace. In this study, we analyzed the relationship between the stable isotopic composition of soil water and precipitation to determine the mechanisms of soil water movement in the small watershed of Quanfuzhuang. We observed significant seasonal variations in soil water sources: antecedent precipitation was the dominant supply during the dry season, and current precipitation dominated during the rainy season. The recharge ratio of precipitation to soil water in the grassland was significantly higher than that in the arbor land and shrubland. The influence of water infiltration, old and new soil water mixing, and soil evaporation on the soil water stable isotopes gradually decreased from the surface (0–20 cm) to the deep (60–80 cm) soil. We observed significant seasonal variability in average soil water δ18O in the upper 0–60 cm and lower variability at 60–100 cm. The average soil water δ18O was generally higher in the dry season than in the rainy season. The mixing of old and new water is a continuous and cumulative process that is impacted by soil structure, soil texture, and precipitation events. We therefore identified a significant time delay in soil water supply with increasing soil depth. Moreover, the piston flow of soil water co-occurred with preferential flow, and the latter was the dominant supply during the rainy season.
Journal Article
Soil Water Dynamics Under Different Land Uses in Loess Hilly Region in China by Stable Isotopic Tracing
Exploring soil water dynamics under different land use types is important for water resource management and vegetation restoration in the Loess Plateau. In this study, we investigated the hydrogen and oxygen isotopic compositions of soil water from four different land use types to explore the mechanism of soil water movement and transformation and analyse the influence of land use. The results show that the range of stable isotopes (δD and δ18O) in soil water was smaller than that in precipitation. Values for δD and δ18O in soil water showed relatively similar temporal variation, heavy isotopes were enriched in the soil water in July and depleted in October. Stable isotope values in shallow (<100 cm depth) soil water and deep (>200 cm depth) soil water were low. The δD and δ18O values in woodlands decreased gradually with increasing depth. Across the four land use types, the maximum variation in δD and δ18O was in the shallow depth of the soil profile. Groundwater was recharged mainly from precipitation and then from soil water. The ratio of groundwater recharge by soil water under different land use types followed this rank order: woodland (35.70%) > grassland (31.14%) > shrubland (29.47%) > cropland (29.18%). Matrix flow and preferential flow coexisted during infiltration, and the occurrence of preferential flow was related to the land use type. The main reason for the variation in isotopic composition in soil water is the difference in soil evaporation, which is influenced by different vegetation cover. Owing to the difference in soil evaporation and fractionation, precipitation on cropland, shrubland, and grassland can recharge more soil water than on woodland.
Journal Article
Study on Spatiotemporal Transport Characteristics of Soil Moisture in Layered Heterogeneous Vadose Zone Based on HYDRAS-3D
The heterogeneity of layered soils affects the transport processes of water in the vadose zone. However, the mechanism of soil moisture transport in the vadose zone under heterogeneous media conditions, especially the three-dimensional transport mechanism, is a frontier problem to be studied. In order to reveal the law of soil water transport in the vadose zone under heterogeneous media, this paper constructs a three-dimensional model of water transport using HYDRAS-3D (V 2.x) software through in situ tests of water transport in 3 × 3 × 4 m sample and verifies and analyzes the model. The vertical distribution and variability of soil water content and the temporal and spatial rules of soil water transversal transport at the soil–layer interface were analyzed. The results indicate that after adjusting the parameters in the HYDRAS-3D model using measured values, the simulation results are reasonable, and the model has high reliability. To represent the water content variability characteristics of the test tube profile, water movement in the vadose zone was classified as follows: (I) steady period (April–September, less affected by rainfall), (II) slow change period (January–March), and (III) rainfall rapid change period (June, when the impact of rainfall on the test cylinder was greater). The two largest values of the soil water potential variation gradient, 19.9 and 17.8 cm/d, were observed in the silty clay layer of the test cylinder, and the influence of evaporation and infiltration in the silty clay layer was most notable at the interface. The lateral transport of soil water at the interface was influenced to a certain degree by the layered heterogeneity, wherein the fine sand layer exhibited the most pronounced impact. This was followed by silt and silty clay layers, with the silt layer showing the lowest degree of influence. The research results can provide scientific reference for the rational planning of water resources in the Yinchuan Plain.
Journal Article
Environmental flow limits to global groundwater pumping
Groundwater is the world’s largest freshwater resource and is critically important for irrigation, and hence for global food security
1
–
3
. Already, unsustainable groundwater pumping exceeds recharge from precipitation and rivers
4
, leading to substantial drops in the levels of groundwater and losses of groundwater from its storage, especially in intensively irrigated regions
5
–
7
. When groundwater levels drop, discharges from groundwater to streams decline, reverse in direction or even stop completely, thereby decreasing streamflow, with potentially devastating effects on aquatic ecosystems. Here we link declines in the levels of groundwater that result from groundwater pumping to decreases in streamflow globally, and estimate where and when environmentally critical streamflows—which are required to maintain healthy ecosystems—will no longer be sustained. We estimate that, by 2050, environmental flow limits will be reached for approximately 42 to 79 per cent of the watersheds in which there is groundwater pumping worldwide, and that this will generally occur before substantial losses in groundwater storage are experienced. Only a small decline in groundwater level is needed to affect streamflow, making our estimates uncertain for streams near a transition to reversed groundwater discharge. However, for many areas, groundwater pumping rates are high and environmental flow limits are known to be severely exceeded. Compared to surface-water use, the effects of groundwater pumping are markedly delayed. Our results thus reveal the current and future environmental legacy of groundwater use.
Estimates for when critical environmental streamflow limits will be reached—with potentially devastating economic and environmental effects—are obtained using a global model that links groundwater pumping with the groundwater flow to rivers.
Journal Article
Tracing stable isotopes (δ2H and δ18O) from meteoric water to groundwater in the Densu River basin of Ghana
This study represents the first attempt to study soil water δ
18
O profiles in Ghana using a mechanical auger. In this paper, the characteristics of δ
18
O and δ
2
H in rain water, surface water, soil water and groundwater have been used to understand the transformation mechanism of rain water to groundwater. Rain waters were sampled in Koforidua and Accra. Surface water and groundwater were sampled from the Densu River and selected boreholes in the basin, respectively. Soil waters were taken from three typical sites, namely, Potroase (POT), Teacher Mante (TM) and Ayikai Doblo (AD) in the northern, middle and southern zone from 0.00- to 6-m depth. The soil water was extracted using vacuum distillation method. The distribution of the stable isotopes of rain water is influenced by rainfall amount with minimal temperature effect. In general, the soil water is of meteoric origin undergoing fractionation-controlled evaporation. In the middle zone, the soil water shows some evidence of recharge from enriched source. The three profiles show similar trend of enriched values in the upper depths with gradual depletions of δ
18
O with depth. The POT profile showed relatively more depleted values suggesting a fast infiltration. In all the three profiles, soil waters below 3 m were found to contribute to groundwater recharge with piston flow as the dominant mechanism. The study also revealed that there is a significant contribution of enrich source to the groundwater system leading to the dilution of the infiltrating water by the large aquifer.
Journal Article
The water footprint of humanity
This study quantifies and maps the water footprint (WF) of humanity at a high spatial resolution. It reports on consumptive use of rainwater (green WF) and ground and surface water (blue WF) and volumes of water polluted (gray WF). Water footprints are estimated per nation from both a production and consumption perspective. International virtual water flows are estimated based on trade in agricultural and industrial commodities. The global annual average WF in the period 1996-2005 was 9,087 Gm³ /y (74% green, 11% blue, 15% gray). Agricultural production contributes 92%. About one-fifth of the global WF relates to production for export. The total volume of international virtual water flows related to trade in agricultural and industrial products was 2,320 Gm³ /y (68% green, 13% blue, 19% gray). The WF of the global average consumer was 1,385 m³ /y. The average consumer in the United States has a WF of 2,842 m³ /y, whereas the average citizens in China and India have WFs of 1,071 and 1,089 m³ /y, respectively. Consumption of cereal products gives the largest contribution to the WF of the average consumer (27%), followed by meat (22%) and milk products (7%). The volume and pattern of consumption and the WF per ton of product of the products consumed are the main factors determining the WF of a consumer. The study illustrates the global dimension of water consumption and pollution by showing that several countries heavily rely on foreign water resources and that many countries have significant impacts on water consumption and pollution elsewhere.
Journal Article