• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Past and Future Changes in Climate and Water Resources in the Lancang–Mekong River Basin: Current Understanding and Future Research Directions

    2022-08-17 01:51:04JunguoLiuDelingChenGnqunMoMsoudIrnnezhdYduPokhrel
    Engineering 2022年6期

    Junguo Liu*, Deling Chen, Gnqun Mo*, Msoud Irnnezhd Ydu Pokhrel

    a School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China

    b Regional Climate Group, Department of Earth Sciences, University of Gothenburg, Gothenburg 405 30, Sweden

    c Department of Civil and Environmental Engineering, Michigan State University, East Lansing, MI 48824, USA

    Keywords:Lancang–Mekong River International river Hydrology Water resources Climate change Hydropower development

    ABSTRACT The Lancang–Mekong River(LMR)is an important transboundary river that originates from the Qinghai–Tibet Plateau, China and flows through six nations before draining into the South China Sea. Knowledge about the past and future changes in climate and water for this basin is critical in order to support regional sustainable development. This paper presents a comprehensive review of the scientific progress that has been made in understanding the changing climate and water systems, and discusses outstanding challenges and future research opportunities. The existing literature suggests that: ①The warming rate in the Lancang–Mekong River Basin(LMRB)is higher than the mean global warming rate,and it is higher in its upper portion, the Lancang River Basin (LRB), than in its lower portion, the Mekong River Basin(MRB); ②historical precipitation has increased over the LMRB, particularly from 1981 to 2010, as the wet season became wetter in the entire basin, while the dry season became wetter in the LRB but drier in the MRB; ③in the past, streamflow increased in the LRB but slightly decreased in the MRB, and increases in streamflow are projected for the future in the LMRB;and ④historical streamflow increased in the dry season but decreased in the wet season from 1960 to 2010,while a slight increase is projected during the wet season.Four research directions are identified as follows:①investigation of the impacts of dams on river flow and local communities;②implementation of a novel water–energy–food–ecology(WEFE) nexus; ③integration of groundwater and human health management with water resource assessment and management; and ④strengthening of transboundary collaboration in order to address sustainable development goals (SDGs).

    1. Introduction

    The Lancang–Mekong River (LMR) is an important transboundary river that originates in the Qinghai–Tibet Plateau region,China and drains to the ocean in the Mekong Delta in Vietnam(Fig.S1 in Appendix A). It is the longest river in Southeast Asia, the seventh longest river in Asia, and the twelfth longest river in the world[1]. Over 70 million people rely on the LMR and its tributaries for water supply,food production,instream transport,and many other services the river system provides to support their livelihoods [2].The Lancang–Mekong River Basin (LMRB) also houses one of the world’s most productive fisheries,and the basin is the second richest in terms of aquatic biodiversity after the Amazon River basin[3,4].

    The length of the LMR is approximately 4880 km [3,4]. In the upper portion of the basin—the Lancang River Basin (LRB)—the river flows from the Qinghai–Tibet Plateau and runs through China’s Qinghai,Yunnan,and the Tibet Autonomous Region,before entering the lower portion of the LMRB—known as the Mekong River Basin (MRB)—at the border between Myanmar and Laos.The Lancang River runs through steep terrains, experiencing an elevation drop of about 4500 m.In the MRB,the river runs through Laos before becoming the border between Laos and Thailand and then re-entering Laos. The river then flows through Cambodia and into Vietnam as a complex delta system before finally draining into the South China Sea [3].

    The LMRB covers an area of 795 000 km2and ranks as the tenth largest river basin in the world in terms of mean annual flow volume [3]. The basin area is shared among China (21%),Myanmar (3%), Laos (25%), Thailand (23%), Cambodia (20%), and Vietnam (8%). The climate of the LMRB is strongly influenced by the Indian summer monsoon, the East Asian monsoon, tropical cyclones, and the El Ni?o–Southern Oscillation (ENSO) [4–6].Annual mean precipitation within the LMRB increases from northwest to southeast [6]. Long-term (1981–2010) mean values of the basin-averaged annual precipitation for the LMRB range from 464 mm?a-1in the LMR to 4300 mm?a-1in the eastern and southeastern parts of the MRB. The annual mean temperature ranges from –4.8 °C in the LMR to 29.0 °C in the southwest region of the MRB [7].

    The mean discharge at the river mouth in the Mekong Delta is about 475 km3?a-1,which provides relatively high water resources per capita for the LMRB in comparison with other large global river basins [3]. Of the total LMRB water resource, approximately 16%comes from the LRB in China, and the rest derives from the MRB,with 35% from Laos, 18% from Thailand, 18% from Cambodia, 11%from Vietnam, and 2% from Myanmar [3]. Despite rich water resources (about 8000 m3?a-1per capita), the high temporal and spatial variabilities in runoff create seasonal water shortages or scarcity [4]. The Qinghai–Tibet Plateau, where the LMR originates,is more sensitive to climate change than other global regions [8],and the hydrological system of the LMRB has also undergone significant changes due to the climate change[9].Furthermore,rapid economic development, growing food demands, and energy needs in riparian countries have led to dramatic land use or land cover changes and alterations of hydrological and ecological systems,particularly due to massive agricultural expansion and hydropower development throughout the LMRB[10].Many studies have indicated that climate change and human activities have substantially altered the LMR streamflow in both its mainstem and tributaries, leading to more frequent extreme events and a longer dry season [11]. Such changes in the hydrologic regime of the LMRB have consequently resulted in the degradation of natural resources in the region—such as fish, water, and land—upon which millions of people in the MRB nations rely [12].

    Given this context,there is an urgent need to better understand the changing climate and water resources in the LMRB in order to support regional transboundary collaborations and synthesize scientific progress and the current status—that is,what we know and what remains unclear. This paper aims to ①synthesize the progress that has been made mostly since the year 2010 in the scientific understanding of the changes in climate and water resources in the LMRB and describe the confidence levels regarding both past and future changes [13]; and ②identify knowledge gaps and opportunities for research that can be used to prioritize future scientific efforts. The information on confidence levels is derived based on the guidance of the Intergovernmental Panel on Climate Change(IPCC)for dealing with uncertainties.More specifically,following the IPCC guidance note on the consistent treatment of uncertainties, three types of consistency of evidence (summary terms:‘‘limited,”‘‘medium,”or‘‘robust”)and three types of degree of agreement (summary terms: ‘‘low,” ‘‘medium,” or ‘‘high”) are used for the evaluation of evidence and agreement among findings from different studies [13]. Based on reviewed literature on climate and water changes, very high confidence is assigned to findings with a high level of agreement and robust evidence. Medium confidence is assigned to findings with either a high level of agreement or robust evidence, and low or very low confidence is assigned to findings with a low level of agreement or limited evidence.

    2. Climate of the LMRB: Historical change and future projections

    2.1. Past and future warming trends

    A list of prior studies focusing on changes in precipitation and temperature over the LMRB and its upper (LRB) and lower (MRB)parts is given in Table S1 in Appendix A. With high confidence,these studies have reported increasing trends in annual mean temperature across the LMRB in the past decades. During 1981–2010,the rate of increase was higher in the LRB(0.6°C?decade-1)than in the MRB (0.2 °C?decade-1) [14]. The warming trends in both the LRB and MRB exceed the global average temperature rise (0.17°C?decade-1) since 1981, as reported by Hartfield et al. [15].

    No statistically significant changes in annual maximum and minimum temperatures were determined over the LRB between the early 1980s and 2010[14],but the annual maximum and minimum temperatures showed the same warming trends as the mean annual temperature in the MRB [7]. The seasonal warming trends showed the highest rate for winter (December–February) across both the LRB [14] and the MRB [7] during 1981–2010. However,studies have reported that the LRB was already experiencing warmer winters before 1981,such as during the period from the 1960s to the early 2000s [16].

    Statistically significant warming trends (0.02 °C?decade-1) in mean annual temperature are expected (with high confidence)over the LMRB during the 21st century [17,18], with a higher rate in the northern and southern parts [19]. However, these temperature projections vary largely depending on the scenario used in the climate models (Table S1). A warming trend (0.01–0.03°C?decade-1) is also projected over the MRB [20], while warming over the LRB is projected to be slightly more evident and consistent[17].The daily maximum temperature over the MRB is expected to increase by 2050,with estimates ranging from 1.6°C in the northern and southwestern parts to 4.1 °C in the southeastern areas,where there is a historically cooler climate than in the central part of the MRB[20].Accordingly,more frequent annual hot days(daily maximum temperature > 33 °C) are projected, particularly in the southern part of the MRB[21].In addition,projections for seasonal temperature changes are fairly homogeneous across the MRB,with a warmer climate projected during wet seasons (1.7–5.3 °C) than during dry seasons (1.5–3.5 °C) for the near future (2020–2050)[20].Meanwhile,daily mean temperatures across the LRB are projected to be higher during dry seasons (7.5–10.5 °C) than during wet seasons (6.0–7.5 °C) under the 6 °C warming scenario [17].Moreover, warmer temperatures, which have historically been observed at lower elevations in the MRB, will be experienced at higher elevations, particularly above 400 m, during this century[20].

    2.2. Uncertainty in estimated past and projected future precipitation

    Previous studies have reported moderately increasing trends in annual precipitation over the LMRB in recent decades (low confidence), accompanied by increased temporal variability [22]. A recent study also reported a wetter but insignificant (p > 0.05)trend of an increased 24.8 mm?decade-1in annual precipitation over the LMRB during 1983–2016 based on daily gridded (0.25° ×0.25°) precipitation data extracted from the precipitation estimation from remote sensing information using an artificial neural network-climate data record (PERSIANN-CDR) [6]. From 1981 to 2007, annual precipitation calculated using the daily gridded(0.25° × 0.25°) Asian precipitation-highly resolved observational data integration toward evaluation of water resources (APHRODITE) data showed a significant (p < 0.05) increasing trend of 52.6 mm?decade-1over the MRB [7]. Similarly, a significant increase (14.5 mm?decade-1) in annual precipitation over the LRB during 1981–2010 was found based on in situ precipitation records at seven meteorological stations [14]. These findings imply that,while there are substantial differences in the estimates based on different datasets, annual precipitation in the LMRB has been increasing in the recent past.The use of various different global climate model (GCM) or regional climate model (RCM) outputs, as well as downscaling methods, could have certain impacts on climate change assessment. In addition, the results could vary depending on carbon dioxide (CO2) emission levels, as considered in the representative concentration pathways (RCPs) [23].

    Employing the gridded (0.25° × 0.25°) monthly data from the Global Precipitation Climatology Center (GPCC), long-term(1901–2013) trend analysis has identified decreases in seasonal precipitation for spring (March–May) and summer (June–August)across the LRB,as well as for summer and fall(September–November)over the MRB[24].For a relatively recent period(1980–2010),Fan and He[14] reported an increasing trend of 8.3 mm?decade-1,only in spring precipitation and over the LRB, by utilizing the monthly precipitation time series measured at seven stations. In addition, a recent study by Chen et al. [25] based on the APHRODITE dataset concluded that, over the entire LMRB, the wet season (May–October, covering the summer months) became wetter by 28 mm?decade-1, and the dry season (November–April,covering the winter months) became drier by 138 mm?decade-1during 1998–2007. Moreover, APHRODITE monthly precipitation data over the LMRB showed increases for July and August (both covered by the wet season) during 1981–2010, while there were small decreases for June and October (covered by the dry season)[7]. These varied estimates indicate a moderate confidence level[13] of changes in precipitation for both the wet and dry seasons in the LMRB (Fig. 1).

    There is a consensus, with high confidence, that there will be significant increases in annual precipitation across the LMRB over the next 30–50 years[18].Variability in annual precipitation is also projected to increase over this basin [17,19,26]. Such a high confidence level of projected wetting trends is primarily due to the indisputable future global warming, which will likely intensify water vapor transport from the Indian Ocean and the Western Pacific Ocean toward the LMRB, resulting in more precipitation across the basin [27]. Depending on the emissions scenario, the projected wetting trends in annual precipitation over the LMRB range from 2.5%–8.6% (under IPCC’s Special Report on Emissions Scenario (SRES) A1b) to 1.2%–5.8% (SRES B1). Annual precipitation is also expected to increase by 35–365 mm(3%–14%)over the MRB by 2050[20]and by approximately 10%over the LRB under the 2°C warming scenario [17]. Monthly precipitation is projected to increase over the LRB for all months by 20%–60% under the 2–6 °C warming scenarios, except for April, which shows a projected 16%–40%decrease[17].With moderate confidence,precipitation is expected to increase during the wet season (May–October) over the MRB by 2050, but is projected to decrease in the dry season(November–April) [20]. Moreover, precipitation will likely experience an elevation shift from high to low altitudes; for example,the annual precipitation of 1500 mm that was historically recorded at an elevation of about 280 m would be observed at elevations of about 80 m [20].

    Fig. 1. Changes in temperature and precipitation over (a) the LMRB, (b) the upper part of the LMRB (the LRB), and (c) the lower part of the LMRB (the MRB), based on the published literature. See Table S1 for more details and the guidance note of the IPCC for the definitions of the different levels of confidence, evidence, and agreement [13].

    3. Water resources in the LMRB: Historical changes and future projections

    3.1. Surface water

    A general downward trend in annual streamflow was found in the LMRB over the time period of 1960–2010, but no clear trend was detected after 2010 [24], although the confidence of such a trend is low. Most studies found a decreasing trend in historical streamflow in the LMRB, while a few studies showed the opposite—that is, an increasing trend in streamflow—due to the differing data and methods applied in each study. A detailed literature review on historical runoff changes is provided in Appendix A Table S2.

    The changes in streamflow are due to the combined impacts of climate change and human activities.The contributions of influential factors vary over different regions and time periods. Climate change was a key driver of the streamflow alterations in the LMRB before 2010, while human activities—mainly dam construction—contributed more after 2010. This finding has been confirmed by both observational[28]and modeling[29]studies.Climate change dictated the changes in annual streamflow during the transition period of 1992–2009 with a contribution of 82.3%, while human activities contributed 61.9% of the changes in the streamflow in the post-impact period of 2010–2014 [28]. In terms of annual streamflow and water-level variations, the hydrological response of the LRB is considered to be more sensitive to climate factors than to human activities when compared with the MRB [30]. This disparity also highlights the accelerating impacts of intensive human activities on the hydrological processes in the area, especially throughout the MRB in recent years [29].

    Differences in the change ratio of streamflow exist between the LRB and MRB because the hydrological systems of these two regions are naturally controlled by different climatic processes[31]. The flow regime in the LRB is influenced more by precipitation and snowmelt,while the flow regime in the MRB is controlled by intense monsoon-season rainfall[32].Climate-induced changes in precipitation increased the streamflow in the LRB [33], while a slightly decreasing trend was found in most of the MRB due to the combined effects of climate change and human activities for the period 1960–2014 [28]. In the LRB, the magnitude and frequency of flood events were found to increase during the period 1961–2001, and this trend is expected to continue throughout the 21st century from 2011 to 2095 [34]. However, the flow regulation by dams in the LRB will potentially reduce such a positive trend in climate-change-induced flood events [35].

    The river flow in the main stem of the LMR is characterized by an inherently strong seasonal cycle due to clear and regular dry–wet transitions.Accordingly,the streamflow seasonality was found to decrease after dam construction in the mainstem of the river[31]. Reservoirs store water in wet seasons and release it during dry seasons,thereby altering the flow regimes[36].The amplitude of the streamflow has generally increased prior to dams being constructed, while a decreasing trend in maximum flows has been found following the completion of dams upstream [28,37]. Dam operation in the basin reduces the flow in wet seasons but increases the streamflow in dry seasons,thus attenuating flow seasonality [29,38]. A study based on observed discharges showed that the cascade of dams in the Lancang River has increased discharge in the dry season by 34% to 155% on average and has reduced discharge in the wet season by 29%–36% at the Chiang Saen station from 1985 to 2010[39].In one of the most important tributaries in the LMRB—that is, the Srepok, Sesan, and Sekong(‘‘3S”) basin, which contributes the most out of all the tributaries to the Mekong River’s discharge—the flow is found to have increased (decreased) by 63%–88% (22%–24.7%) in the dry (wet)season between 1986 and 2005 due to dam construction [40,41].The annual discharge of the 3S basin is projected to increase by 10.7%, 14.8%, and 13.9%under Representative Concentration Pathway 4.5 (RCP4.5) for the 2030s, 2060s, and 2090s, respectively,compared with the baseline period of 2000–2005 [42].

    Despite the decrease in streamflow seasonality, streamflow variability has been found to have increased in the dry season along the river from upstream to downstream due to the combined effects of different reservoir operation plans and land cover changes in the LMRB[38,43].Consequently,flood amplitude,duration,and the maximum water level have decreased throughout the basin [28,31,32], causing a significant delay in the start, peak, and end of the seasonal flood pulse [39]. These changes in the flood dynamics are expected to amplify if many of the large, planned dams are constructed in the mainstem of the Mekong River, and will particularly affect the flood dynamics in the Tonlé Sap Lake and Mekong Delta systems [44]. Such changes in the flood pulse can help to prevent flood disasters,but can have potential impacts on aquatic biodiversity[45].Aside from dam construction-induced changes in the flow regime,large-scale atmospheric processes such as radiation,convection,and aerosol movement increased the likelihood of extreme floods and low flows during the 1924–2000 period [31].

    Along with climate change and dam construction,other human activities such as irrigation and cropland expansion have altered the water resources in the LMRB. Studies have shown that,although basin-scale average changes in streamflow due to cropland expansion and irrigation are small, changes over highly irrigated areas—mostly in the downstream region of the MRB—are significant [36]. The total water withdrawal from the entire LMRB has been reported to be approximately 62 km3—that is, 13%of the average annual discharge—of which Vietnam, Thailand, China,Laos, Cambodia, and Myanmar account for approximately 52%,29%, 9%, 5%, 3%, and 2%, respectively [46]. On average, surface water withdrawal accounts for 97% of the total water withdrawal from the basin, while groundwater withdrawal represents 3% of the total water withdrawal [46]. In the MRB, approximately 80%–90%of water abstractions is utilized for agriculture,but the annual water utilization for agriculture is still less than 4% of the total annual streamflow in this region [47].

    Despite the use of different climate forcing and models,studies project—with high confidence—an increasing trend for streamflow in the LMRB;however,the flow regime is highly susceptible to different drivers, such as dam construction, irrigation expansion,land-use change, and climate change. Substantial changes are expected in both annual and seasonal flow, along with a general increasing trend[38,48].Although hydropower development exhibits a limited influence on total annual flows,it has the largest seasonal impact on streamflow,with an increase in the dry season and a decrease in the wet season,outweighing the impacts of the other drivers [48]. One study showed that climate change may increase the annual streamflow by 15%, while irrigation expansions would cause a slight decrease in the annual streamflow of 3% over the period of 2036–2065 compared with the period of 1971–2000.This study was based on statistically downscaled data from the Coupled Model Intercomparison Project Phase 5 (CMIP5) and used a distributed hydrological model, VMod, with a spatial resolution of 0.5 degrees (~50 km at the equator) [48]. The changing ratio in the dry season(+70%)exceeds the changing ratio in the wet season(–15%).In the 3S tributary,the streamflow is projected to increase by 96% in the dry season and decrease by 25% in the wet season,which indicates a higher streamflow sensitivity to climate change and human activities in the 3S system than in the entire LMRB[49].

    The scenarios for streamflow changes vary spatially, especially in the MRB[50].Although an increasing trend in streamflow is projected for the LMRB in future,the uncertainties in these projections remain large.Studies based on 11 GCMs show that the annual runoff is projected to increase by 21%,with a range from–8%to 90%by the 2030s in comparison with the historical period (1951–2000)[51]. However, V?stil? et al. [21] reported only a 4% increase in annual flow by the 2040s in the LMRB.These authors used dynamically downscaled data from the ECHAM4 climate model to drive a distributed hydrological model Variable Infiltration Capacity (VIC)at a spatial resolution of 25 km. Other studies, based on CMIP5 datasets for the near future (2036–2065), have also reported relatively small changes in mean annual flow ranging from 3% to 10%in the LMRB [21,52].

    The magnitude and frequency of extremely high-flow events are projected to increase, while low-flow events are projected to occur less frequently, based on investigations focusing only on the impacts of climate change [52]. More frequent extreme highflow events could exacerbate flood risks in the LMRB.The massive hydropower construction that induced changes in discharge is expected to have a greater effect on the hydrography than climate change over the next 20–30 years[19].Furthermore,different patterns of water changes may be present in future in different subbasins of the LMRB. The number of wet days is also projected to increase by the end of the 21st century (2080–2099), which could further increase the flood risk but benefit water utilization in dry periods [53]. The expected changing ratio has been found to be location dependent. For example, Hoang et al. [52] showed that the annual streamflow change in subbasins ranged from +5% to+16%, depending on location, in the period of 2036–2065, in comparison with the baseline of 1971–2000. A detailed summary of changes in historical and future streamflow is shown in Fig. 2.

    3.2. Groundwater

    Groundwater is a crucial water resource in the LMRB [31]. It connects the farming system, wetland ecology, and livelihood of more than 4.5 million people in the Mekong Delta who rely on the groundwater for drinking [54]. It also plays a critical role in preventing saltwater intrusion [55]. In general, the groundwater in the LMRB has not previously been investigated sufficiently.Only limited information on some local areas within the MRB can be found in the literature related to groundwater resource size, use,and quality [51].

    Fig.2. Changes in streamflow over(a)the LMRB,(b)the LRB,and(c)the MRB,based on published works listed in Appendix A Table S3.Other details are the same as for Fig.1.

    The Mekong Delta extends from central Cambodia to the South China Sea and covers 50 000 km2of the fertile alluvial plain[55].In the delta region, more than one million wells have been built to extract groundwater for agricultural, domestic, and industrial needs. Recently, the number of wells in the delta area increased dramatically from the limited number that existed before the 1960s [56]. Based on global groundwater data from the inventory of the International Groundwater Resources Assessment Center(IGRAC), approximately 0.55 km3of groundwater was extracted from the LMRB (mainly from the MRB) in 2000 [57]. However, it has been revealed that this number is significantly lower than that reported in country-based statistics[58].The reason for this difference might be that the groundwater used by individual households across the basin may not have been reflected in the global database from the IGRAC [31].

    The groundwater system in the LMRB is primarily affected by the changing hydrological system and by intensive human activities that alter the groundwater balance in terms of recharge and withdrawal [59]. Based on 30 years of monitoring data in the Mekong Delta, a significant decline in the groundwater level was found in this region [55]. In particular, the groundwater level in Ca Mau Province (Vietnam) has fallen by as much as 10 m since 1995 [55]. Groundwater levels have also been observed to be persistently declining in Vietnam at a rate of approximately 0.3 m?a-1,based on data from nested monitoring wells, causing land subsidence in this region at an average rate of approximately 1.6 cm?a-1[60].

    The major driving factors of such decreasing trends in groundwater levels can be explained by increased water demand and reduced water supply [55]. Growing populations and expanding agriculture have resulted in a high demand for freshwater; this intensifies the exploitation of groundwater,and the supply of clean water is lower in this region [55]. The reduced groundwater recharge is mainly caused by land-use changes,including a reduction in forests and an increase in the cultivation of fields,where the groundwater recharge ratio is reduced accordingly [59]. Some studies have reported that dams may have a positive impact on the groundwater system due to the artificially controlled,relatively high water level that dams ensure during the dry season [31]. In general, groundwater systems can be impacted by the dynamics of terrestrial water storage due to water impoundment behind dams and can further offset sea-level rise [61], thereby limiting salinity intrusion [62]. Moreover, relatively high groundwater levels due to higher, damming-induced dry-season water levels could benefit irrigation systems in terms of energy cost reduction[31].In addition to the impacts of multiple factors on groundwater quantity, sea-level-induced saltwater intrusion, agrochemical use,and inherent arsenic pollution affect the quality of groundwater in the region[56,60,63].The overuse of groundwater has also been found to exacerbate arsenic contamination in groundwater in the Mekong Delta [64], which could be further intensified by climate change [51].

    Climate change-induced changes in downstream flood pulse and groundwater recharge patterns are also expected to impact the groundwater system in the LMRB in the future [65]. However,similar to the observed groundwater alterations,projected groundwater information in the LMRB is limited.Shrestha et al. [66]conducted a study on the Mekong Delta and analyzed groundwater change under different RCP scenarios. Their results show that groundwater recharge will decrease at a rate of 3 mm?a-1under RCP8.5 and 1.3 mm?a-1under RCP4.5 by the end of the 21st century,in comparison with the groundwater recharge in 2010.Moreover, the groundwater level is projected to decline by 1.5–41.0 m(depending on the location) by the end of the 21st century. This decline could affect groundwater storage in this region [66],although a recent global modeling study has suggested that groundwater recharge under different future warming levels would increase, especially in parts of the MRB [67].

    3.3. Potential environmental and social impacts of water resource changes

    Substantial changes in the water resources in the LMRB will likely have crucial implications for sustainable water management.Projected changes in the basin flow regime are likely to have negative consequences in many aspects. First, large alterations to flow regimes will create disturbances to aquatic ecosystems by changing the distribution of vegetation, natural habitats of native species, and fish migrations patterns [68–70]. Changes in the flow regime caused by dams are also expected to profoundly alter fish abundance and catch in the lower portions of the MRB,with implications for dietary protein consumption [71]. Decreased streamflow in the river during the wet season could impede the overland water flows that induce the natural sedimentation process on floodplains, affecting flood-recession agriculture. Reduced sedimentation will decrease the nutrients carried by the sediment during flood events, thereby further impacting crop yields [48].

    It is estimated that water use in the LMRB will increase significantly due to rapid socioeconomic development and growing populations,which are occurring more rapidly than the increase in available water resources in this area [51]. This could result in growing water security challenges in the near future, with an increase in the number of exposed people due to water stress. In addition, studies have revealed that the hotspot areas of water scarcity tend to travel downstream in regions where flows are significantly regulated by dams [72].

    The demand for groundwater in the LMRB is expected to increase dramatically under climate change, since surface water is projected to likely become less accessible, intensifying the groundwater withdrawal in this region [51]. Intense extraction of groundwater could also result in large-scale land subsidence,which could lead to the release of arsenic in deep groundwater through vertical migration[73].This will limit crop yields and pose serious human health risks in the future [74].

    In addition to the negative effects of an altered water system,some positive impacts should be mentioned. For example, the increase in streamflow during the dry season[29]could effectively help to overcome water stress for agriculture [75]. The relatively high water level during the dry season allows for the prevention of saltwater intrusion downstream,especially in the Mekong Delta[3,65].Furthermore,relatively low,dam-induced water levels during the wet season are likely to result in lower flood risks along the river,especially in the main floodplains on the Mekong Delta[44].

    4. Knowledge gaps and future research opportunities

    4.1. Impacts of dams on river flow and local communities

    Dams and their impacts have become a hot topic under frequent discussion in the scientific literature and public media[76],which often leads to controversies. In the LMRB, dams provide multiple services for local communities, including irrigation, hydropower,and navigation facilities, of which hydropower—the colossus of the renewable energy world—draws the most attention [4]. Since the vast hydropower potential of the river system has been exploited to a limited extent so far, especially in the MRB, the MRB countries are undertaking ambitious plans to develop largescale hydropower projects[77].Hydropower helps to meet the rising energy demand and promotes economic development in riparian countries [78]. However, it also has negative impacts on the environment and local livelihoods. Such impacts arise from the direct and profound alteration of flow regimes, inundation patterns, and sediment processes downstream [2].

    Furthermore, many hydropower development activities have focused on energy benefits without considering the numerous and long-lasting implications to local livelihoods and ecosystem services.With the impacts of the relatively small number of mainstem dams already being felt downstream [29,79], it is crucial to gain an improved understanding of how the development of a large number of planned dams would affect downstream societies and ecosystems. One such area is the Tonlé Sap Lake region, where ecosystems and local livelihoods largely depend on the unique flow reversal in the Tonlé Sap River that is made possible by the flood pulse in the mainstem Mekong River [80]. This flow reversal might cease if many of the projected dams are built[44];however,there is a lack of a quantitative understanding of the compounded downstream effects of climate change and upstream dams.

    4.2. The water–energy–food–ecology nexus

    The water–energy–food (WEF)nexus has attracted attention in recent years due to its potential to help develop an understanding of synergies and tradeoffs in an interdisciplinary way among the many frameworks or paradigms for promoting sustainable development [81]. Many studies have taken the WEF nexus approach to improve the understanding and quantification of the supply and demand of the natural resources, economic flows, and social structures that affect water, energy, and food securities in the LMRB[82].The burgeoning population in this region,accompanied by rapid socioeconomic growth, is expected to cause a surge in demand for water, energy, and food, posing additional challenges for regional sustainability in the future [83]. The WEF nexus will be a promising paradigm to address these challenges. However,achieving WEF securities takes more than just addressing the demand and supply dynamics. More attention needs to be paid to sustaining and restoring the ecosystems that support the provisioning of natural resources in order to maintain societal resilience and ecological well-being [84].

    The main goal of the WEF nexus is to integrate water, energy,and food securities,all of which depend on the capability of human societies to organize themselves in such a way as to manage natural resources. Water, energy, and food security can negatively interact with other environmental factors, such as biodiversity and ecosystem services, thereby threatening the long-term sustainable supply of natural resources [85]. Furthermore, ecological well-being is crucial in order to safeguard healthy landscapes that provide a balance of the functions that support the provision of sustainable resources[86].Therefore,ecology is a promising factor for improving water,energy,and food securities,and should form a fourth fundamental dimension of a novel water–energy–food–ecology (WEFE) nexus framework. The key principles of this new paradigm are to integrate the role of ecology into nexus thinking and to engage local communities in nature-based solutions.

    4.3. Groundwater assessment and human health

    Groundwater, which supplies drinking water, industrial water use, and irrigation, has been considered a critical water resource in the LMRB, especially in the Mekong Delta region, as a supplement to surface water resources [55]. In Cambodia and Thailand,groundwater is even used as a major water resource for drinking water supply [87]. Moreover, increased groundwater exploitation is occurring due to growing industrial and agricultural uses [58].However, studies on groundwater resource assessments have received far less attention than studies on surface water systems[31]. Only limited information exists on the extent and size of the aquifer systems around the Mekong Delta [51].

    The demand for groundwater has substantially increased in the LMRB due to the rapid socioeconomic development in recent years and the reduction in surface water resources as a result of climate change and anthropogenic activities [55]. In some regions, the overexploitation of groundwater, together with climate change,has already caused widespread environmental problems, such as water-quality deterioration, saltwater intrusion, and aquifer storage depletion [56,60,63,65,74]. The compounded effects on the groundwater system might be far more complex.In addition,overuse of groundwater has been found to exacerbate arsenic contamination in groundwater,causing serious health problems in parts of Cambodia and Vietnam [88,89]. Most likely, climate change will further exacerbate these arsenic problems [90,91]. Therefore, a holistic and thorough analysis of water resources that integrates groundwater and human health is both necessary and imperative in order to provide a clear picture of the multitude of hydrological,ecological, health, and socioeconomic effects that may be imminent under a changing climate, socioeconomic growth, and shifts in water management.

    4.4. Transboundary collaboration to address sustainable development goals

    Acting toward sustainable development goals(SDGs)is of great importance for the LMRB, where approximately 40% of people in the region live in poverty[4]and 70%of the people in the Mekong Delta suffer from safe water shortage[92].Efforts have been made in recent years by the riparian countries in the basin to implement SDGs, including ①the Water Resources Management Strategic Plan 2015–2026 for SDG 6 (Clean Water and Sanitation); ②the 20-Year Integrated Energy Plan for SDG 7 (Affordable and Clean Energy); and ③the Climate Change Master Plan 2015–2036 for SDG 13 (Climate Action) [93]. The LMRB is still far from meeting most of the SDGs, particularly SDG 3 (Good Health and Well-Being), SDG 9 (Industry, Innovation, and Infrastructure), SDG 2(Zero Hunger), and SDG 1 (End Poverty) [94].

    In the LMRB, water links most of the SDGs and plays a central role in the interactions between SDGs (both tradeoffs and synergies), such as energy, food, and health [4]. However, the basin faces numerous challenges for sustainable regional development because of varying water supply and demand among the riparian countries, as well as differences in their interest in basin management and infrastructural development,such as the construction of large-scale hydropower dams. This has made the LMRB one of the most contested international river basins in the world.These challenges underscore the need for an effective cooperation mechanism and a water resource development plan to avoid disputes over water benefits-sharing among stakeholders [95]. This situation, by far, could be the biggest obstacle to achieving SDGs in the LMRB. Therefore, transboundary cooperation, involving policy interventions from different ministerial remits, is necessary in order to strengthen synergies among stakeholders and align their agenda toward achieving SDGs in the basin.

    5. Summary

    In this paper, we presented a comprehensive review of the existing body of literature addressing changes in the climate and water resources in the LMRB under unequivocal global warming for both historical and future periods. We conclude that there is a critical need to better understand the changing climate and hydrological systems in the LMRB and the socioeconomic and ecological consequences of achieving SDGs in the LMRB, which features a high density of human activities, vulnerable infrastructure, and poor land-use management and practices.Despite the tremendous progress that has been made in understanding both the climatological and hydrological features of the LMRB, scientific communities, societies, and governments are still in need of theoretical and practical knowledge that can help mitigate regional and/or global environmental change while improving socioeconomic and environmental sustainability. Some of the biggest and most pressing challenges are related to the following urgent tasks include: ①investigation of the impacts of dams on river flow and local communities; ②implementation of a novel WEFE nexus; ③integration of groundwater and human health considerations into water resource assessment and management;and ④strengthening of transboundary collaboration in order to address SDGs.To cope with and overcome these serious challenges,international collaborations among governments, scientists, and the public are critically important.Such collaborations must generate new knowledge based on an interdisciplinary ‘‘web” model,instead of a disciplinary ‘‘tree” model, in order to play a key role in moving toward achieving SDGs in the LMRB [96].

    This review is based on existing articles,which implies that the outcome of the assessment depends on what is publicly available.As an example, it would be desirable—if the literature allows—to perform an analysis that separates the natural and regulated flow.However, a limited number of articles exist on future projections regarding the natural and regulated flow in the LMRB.Future studies could focus on developing a comprehensive analysis of the individual and compounded effects of climate change and dams on water resources, ecosystems, and societies, with a particular emphasis on upstream–downstream linkages, which are crucial for transboundary water management and regional sustainability within the LMRB.

    Acknowledgments

    This research has been supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA20060402),the National Natural Science Foundation of China(41625001 and 41571022), the Pengcheng Scholar Program of Shenzhen, the National High-Level Talents Special Support Plan(‘‘Ten Thousand Talents Plan”), the High-level Special Funding of the Southern University of Science and Technology (G02296302 and G02296402),the Leading Innovative Talent Program for young and middle-aged scholars by the Ministry of Science and Technology, and the National Science Foundation (CAREER Award;1752729).

    Compliance with ethics guidelines

    Junguo Liu, Deliang Chen, Ganquan Mao, Masoud Irannezhad,and Yadu Pokhrel declare that they have no conflict of interest or financial conflicts to disclose.

    Appendix A. Supplementary data

    Supplementary data to this article can be found online at https://doi.org/10.1016/j.eng.2021.06.026.

    18禁在线无遮挡免费观看视频| 精品国产三级普通话版| 亚洲精品,欧美精品| 欧美日韩在线观看h| 久久99精品国语久久久| 最新中文字幕久久久久| 美女大奶头视频| 久久久午夜欧美精品| 国产av在哪里看| 汤姆久久久久久久影院中文字幕 | 国产精品av视频在线免费观看| av国产免费在线观看| 久久99蜜桃精品久久| 国产av码专区亚洲av| 欧美高清成人免费视频www| 精品少妇黑人巨大在线播放| 国产伦在线观看视频一区| 国产又色又爽无遮挡免| 国产成人午夜福利电影在线观看| av在线亚洲专区| 夜夜爽夜夜爽视频| 日韩在线高清观看一区二区三区| 不卡视频在线观看欧美| 人妻制服诱惑在线中文字幕| 欧美最新免费一区二区三区| 色网站视频免费| 麻豆久久精品国产亚洲av| av网站免费在线观看视频 | 在线免费观看的www视频| 97超视频在线观看视频| 亚洲自偷自拍三级| 夫妻午夜视频| 国产高清国产精品国产三级 | 国产午夜精品论理片| 免费看光身美女| 一个人看的www免费观看视频| 99久久九九国产精品国产免费| 国产有黄有色有爽视频| 日本免费在线观看一区| 精品一区二区三区人妻视频| 欧美精品一区二区大全| 中文欧美无线码| 国产精品国产三级国产av玫瑰| 久久精品综合一区二区三区| 国产成人a∨麻豆精品| 一本一本综合久久| 99热这里只有是精品在线观看| 精品久久久久久久久久久久久| 97超碰精品成人国产| 亚洲av二区三区四区| 纵有疾风起免费观看全集完整版 | 少妇裸体淫交视频免费看高清| 大片免费播放器 马上看| 三级毛片av免费| 九九爱精品视频在线观看| 午夜视频国产福利| 看十八女毛片水多多多| 亚洲欧美一区二区三区黑人 | 波多野结衣巨乳人妻| 国产成人一区二区在线| 黄色配什么色好看| 国产精品久久久久久久电影| 中文字幕av成人在线电影| 97热精品久久久久久| 亚洲国产色片| 超碰97精品在线观看| 99久久人妻综合| 成人综合一区亚洲| 久久久久国产网址| 两个人的视频大全免费| 久久久亚洲精品成人影院| 26uuu在线亚洲综合色| 国产成人精品婷婷| 91久久精品国产一区二区三区| av在线播放精品| 最近手机中文字幕大全| 精品人妻熟女av久视频| 女人被狂操c到高潮| 亚洲精品一区蜜桃| 午夜免费观看性视频| 欧美激情国产日韩精品一区| 亚洲成人av在线免费| 久久久久久九九精品二区国产| 美女主播在线视频| 日韩制服骚丝袜av| 国产精品国产三级国产av玫瑰| 国产高清国产精品国产三级 | 精品一区二区三区人妻视频| 日本午夜av视频| 美女主播在线视频| 国产成人福利小说| 男女视频在线观看网站免费| 男人和女人高潮做爰伦理| 国产精品一二三区在线看| 国产91av在线免费观看| 欧美97在线视频| 国内精品一区二区在线观看| 两个人的视频大全免费| 亚洲欧洲国产日韩| 日本猛色少妇xxxxx猛交久久| 啦啦啦中文免费视频观看日本| 一本久久精品| a级毛色黄片| 国产淫语在线视频| 黄色一级大片看看| 国内精品美女久久久久久| 黄片无遮挡物在线观看| 亚洲av福利一区| 两个人视频免费观看高清| 亚洲成人久久爱视频| 午夜福利成人在线免费观看| 日韩视频在线欧美| 欧美人与善性xxx| 国内精品美女久久久久久| 日本与韩国留学比较| 一级毛片 在线播放| 欧美一区二区亚洲| 精品久久久精品久久久| 国产69精品久久久久777片| 特大巨黑吊av在线直播| 成人综合一区亚洲| www.av在线官网国产| 亚洲精品乱码久久久久久按摩| 美女大奶头视频| 亚洲精品色激情综合| 亚洲av电影在线观看一区二区三区 | 久久草成人影院| 午夜精品一区二区三区免费看| 亚洲精品一二三| 国产老妇女一区| 91久久精品电影网| 亚洲av.av天堂| 麻豆国产97在线/欧美| 毛片一级片免费看久久久久| 久久人人爽人人片av| 又爽又黄a免费视频| 91狼人影院| 亚洲电影在线观看av| 国产不卡一卡二| 亚洲精品乱久久久久久| 超碰av人人做人人爽久久| 2021少妇久久久久久久久久久| 99久国产av精品| 夜夜爽夜夜爽视频| 波野结衣二区三区在线| 国产精品综合久久久久久久免费| 国产真实伦视频高清在线观看| 国产精品一区二区三区四区久久| 天美传媒精品一区二区| 2021少妇久久久久久久久久久| 亚洲精品中文字幕在线视频 | 国产高清三级在线| 亚洲成色77777| 亚洲自拍偷在线| 国产亚洲午夜精品一区二区久久 | 成人性生交大片免费视频hd| 日韩欧美国产在线观看| 少妇高潮的动态图| 久久99蜜桃精品久久| 国国产精品蜜臀av免费| 国模一区二区三区四区视频| 亚洲精品456在线播放app| 欧美潮喷喷水| 三级男女做爰猛烈吃奶摸视频| 欧美日韩在线观看h| 亚州av有码| 精品久久久精品久久久| 久久久久久久国产电影| 国产伦理片在线播放av一区| 午夜福利在线在线| 激情五月婷婷亚洲| av一本久久久久| 淫秽高清视频在线观看| 国产在视频线精品| 国产久久久一区二区三区| 国产精品人妻久久久久久| ponron亚洲| 99热网站在线观看| 亚洲aⅴ乱码一区二区在线播放| 婷婷色av中文字幕| 国产又色又爽无遮挡免| 国产高潮美女av| 热99在线观看视频| 嫩草影院精品99| 日韩亚洲欧美综合| 天堂影院成人在线观看| www.av在线官网国产| 人人妻人人澡欧美一区二区| 男女国产视频网站| 男人爽女人下面视频在线观看| 天堂影院成人在线观看| .国产精品久久| 最新中文字幕久久久久| 丝袜美腿在线中文| 成人二区视频| 久久久久久久久久成人| 国产爱豆传媒在线观看| 国产欧美另类精品又又久久亚洲欧美| 美女内射精品一级片tv| 蜜桃亚洲精品一区二区三区| 国产又色又爽无遮挡免| 男女啪啪激烈高潮av片| 麻豆国产97在线/欧美| 亚洲av免费高清在线观看| 精品人妻一区二区三区麻豆| 成人亚洲欧美一区二区av| 亚洲熟女精品中文字幕| or卡值多少钱| 日韩一区二区三区影片| 97超碰精品成人国产| 久久久午夜欧美精品| 五月玫瑰六月丁香| 好男人在线观看高清免费视频| 国产色爽女视频免费观看| 一个人看的www免费观看视频| 精品国产三级普通话版| 69人妻影院| 久久人人爽人人片av| 亚洲在线自拍视频| 午夜福利在线观看免费完整高清在| 久久久久久伊人网av| 丰满少妇做爰视频| 午夜久久久久精精品| 99视频精品全部免费 在线| 久久99热这里只有精品18| 欧美激情在线99| 久久久久久久大尺度免费视频| www.av在线官网国产| 精华霜和精华液先用哪个| 听说在线观看完整版免费高清| 最近的中文字幕免费完整| 免费人成在线观看视频色| 寂寞人妻少妇视频99o| 国产一区亚洲一区在线观看| 午夜福利在线观看吧| 亚洲久久久久久中文字幕| 国产黄片美女视频| 草草在线视频免费看| 日韩成人av中文字幕在线观看| 久久精品国产亚洲网站| 亚洲人成网站在线观看播放| 精品人妻偷拍中文字幕| 亚洲熟妇中文字幕五十中出| 在线 av 中文字幕| 国产伦精品一区二区三区四那| 国产一级毛片七仙女欲春2| 欧美精品国产亚洲| 97精品久久久久久久久久精品| 日韩一区二区视频免费看| 久久热精品热| 国产黄a三级三级三级人| 亚洲国产色片| 联通29元200g的流量卡| av网站免费在线观看视频 | 亚洲av免费高清在线观看| 日本三级黄在线观看| 国产精品一区二区在线观看99 | 国模一区二区三区四区视频| 久久精品国产鲁丝片午夜精品| 人人妻人人澡人人爽人人夜夜 | 一级毛片久久久久久久久女| 国产精品国产三级国产专区5o| 欧美高清成人免费视频www| 亚洲国产精品sss在线观看| 午夜激情久久久久久久| 18禁裸乳无遮挡免费网站照片| 免费黄频网站在线观看国产| 国内少妇人妻偷人精品xxx网站| 久久精品综合一区二区三区| 最近的中文字幕免费完整| 国产午夜精品一二区理论片| freevideosex欧美| 国产精品女同一区二区软件| 国产精品美女特级片免费视频播放器| 可以在线观看毛片的网站| 亚洲精品aⅴ在线观看| 国产精品日韩av在线免费观看| 97精品久久久久久久久久精品| 久久久久免费精品人妻一区二区| 亚洲成人精品中文字幕电影| 国精品久久久久久国模美| 国产乱人偷精品视频| 大话2 男鬼变身卡| 久久精品综合一区二区三区| 亚洲精品成人av观看孕妇| 人妻一区二区av| 国产 一区精品| 国精品久久久久久国模美| 精品亚洲乱码少妇综合久久| 夜夜看夜夜爽夜夜摸| 床上黄色一级片| 成年免费大片在线观看| 日韩在线高清观看一区二区三区| 国产精品国产三级专区第一集| 日日干狠狠操夜夜爽| 乱码一卡2卡4卡精品| 麻豆久久精品国产亚洲av| 亚洲国产欧美人成| 韩国av在线不卡| 中文资源天堂在线| 久久精品国产鲁丝片午夜精品| 日韩国内少妇激情av| 亚洲美女视频黄频| 日本欧美国产在线视频| 午夜视频国产福利| 91aial.com中文字幕在线观看| 两个人视频免费观看高清| 亚洲精品乱码久久久v下载方式| 你懂的网址亚洲精品在线观看| 亚洲欧洲日产国产| 免费看av在线观看网站| 女人久久www免费人成看片| 亚洲怡红院男人天堂| 99久久精品国产国产毛片| 亚洲av日韩在线播放| 久久久精品欧美日韩精品| 91精品国产九色| 在线a可以看的网站| 亚洲一级一片aⅴ在线观看| 51国产日韩欧美| 少妇熟女aⅴ在线视频| 最近最新中文字幕免费大全7| 亚洲欧美一区二区三区国产| 国产成人一区二区在线| 国产成人91sexporn| 中文乱码字字幕精品一区二区三区 | 日本免费在线观看一区| 国产黄a三级三级三级人| 久久99热6这里只有精品| 亚洲经典国产精华液单| 国产一区亚洲一区在线观看| 免费在线观看成人毛片| 免费看光身美女| 我的女老师完整版在线观看| 人妻少妇偷人精品九色| 日本熟妇午夜| 美女黄网站色视频| 国产成人aa在线观看| 女人久久www免费人成看片| 亚洲av成人av| 成年免费大片在线观看| 插逼视频在线观看| 淫秽高清视频在线观看| 精品99又大又爽又粗少妇毛片| 午夜福利在线观看免费完整高清在| 我要看日韩黄色一级片| 熟妇人妻不卡中文字幕| 人妻夜夜爽99麻豆av| 美女xxoo啪啪120秒动态图| 99久久人妻综合| 边亲边吃奶的免费视频| 视频中文字幕在线观看| 久久久a久久爽久久v久久| 2021天堂中文幕一二区在线观| 插阴视频在线观看视频| 亚洲av中文字字幕乱码综合| 国产真实伦视频高清在线观看| 亚洲精品国产av成人精品| 精品久久久久久久人妻蜜臀av| 日韩不卡一区二区三区视频在线| 国产精品久久久久久精品电影小说 | 人人妻人人澡欧美一区二区| 午夜老司机福利剧场| 尤物成人国产欧美一区二区三区| 成人毛片a级毛片在线播放| 搡老妇女老女人老熟妇| 国产日韩欧美在线精品| 亚洲欧美日韩无卡精品| 国语对白做爰xxxⅹ性视频网站| 国产午夜精品一二区理论片| 五月伊人婷婷丁香| 精品一区二区三区视频在线| 国产成人午夜福利电影在线观看| 亚洲欧美成人综合另类久久久| 国产麻豆成人av免费视频| 九草在线视频观看| 又粗又硬又长又爽又黄的视频| 男人狂女人下面高潮的视频| 国产午夜福利久久久久久| 校园人妻丝袜中文字幕| 国产探花在线观看一区二区| 亚洲av成人精品一二三区| 最近的中文字幕免费完整| av天堂中文字幕网| 亚洲最大成人av| 亚洲天堂国产精品一区在线| 欧美三级亚洲精品| 久久99热这里只频精品6学生| 99热这里只有是精品50| 日本午夜av视频| 亚洲欧美中文字幕日韩二区| 成人亚洲精品一区在线观看 | 男人狂女人下面高潮的视频| 三级国产精品欧美在线观看| 日本免费a在线| 国产成人精品一,二区| 欧美bdsm另类| 亚洲四区av| 国产白丝娇喘喷水9色精品| 日本猛色少妇xxxxx猛交久久| 亚洲av电影不卡..在线观看| 国产免费福利视频在线观看| 日日干狠狠操夜夜爽| av专区在线播放| 国产精品av视频在线免费观看| 国产乱来视频区| 亚洲电影在线观看av| 青青草视频在线视频观看| 大又大粗又爽又黄少妇毛片口| 久久精品国产自在天天线| 日韩 亚洲 欧美在线| 免费看光身美女| 夫妻午夜视频| av黄色大香蕉| 欧美日韩在线观看h| 久久久色成人| 色综合色国产| 色综合站精品国产| 亚洲久久久久久中文字幕| 自拍偷自拍亚洲精品老妇| 精品一区二区三区视频在线| 网址你懂的国产日韩在线| 日本猛色少妇xxxxx猛交久久| 熟妇人妻不卡中文字幕| 中文字幕av成人在线电影| 亚洲精品国产av成人精品| 亚洲在久久综合| 精品久久久久久久久av| 丝袜喷水一区| 哪个播放器可以免费观看大片| 91精品伊人久久大香线蕉| 免费看不卡的av| 天堂√8在线中文| 99热这里只有精品一区| 自拍偷自拍亚洲精品老妇| 99久久精品国产国产毛片| 国产黄片美女视频| 久久综合国产亚洲精品| 啦啦啦韩国在线观看视频| 国产精品久久久久久精品电影| 精品一区二区三区视频在线| av天堂中文字幕网| 国产av国产精品国产| 精品久久久久久久人妻蜜臀av| av在线观看视频网站免费| 一本—道久久a久久精品蜜桃钙片 精品乱码久久久久久99久播 | 亚洲内射少妇av| 久久精品国产鲁丝片午夜精品| 国产精品国产三级专区第一集| av女优亚洲男人天堂| 在线a可以看的网站| 最近中文字幕高清免费大全6| 日日摸夜夜添夜夜添av毛片| 男女边吃奶边做爰视频| 国产色爽女视频免费观看| 日韩伦理黄色片| 久久精品久久久久久久性| 久久精品人妻少妇| 99久久精品国产国产毛片| 伦理电影大哥的女人| 亚洲av一区综合| 国产又色又爽无遮挡免| 日韩大片免费观看网站| 日本三级黄在线观看| 又大又黄又爽视频免费| 国产成人aa在线观看| 夜夜看夜夜爽夜夜摸| 日韩欧美精品免费久久| 精品酒店卫生间| 校园人妻丝袜中文字幕| av在线亚洲专区| 色综合站精品国产| 欧美潮喷喷水| 亚州av有码| 亚洲天堂国产精品一区在线| 搡女人真爽免费视频火全软件| 亚洲精品456在线播放app| 亚洲真实伦在线观看| 国产黄色视频一区二区在线观看| 亚洲欧美一区二区三区黑人 | 淫秽高清视频在线观看| 国产淫语在线视频| 久久久久久久久久黄片| av线在线观看网站| 久久久久精品久久久久真实原创| 国产亚洲一区二区精品| 婷婷色麻豆天堂久久| 少妇人妻精品综合一区二区| 欧美精品一区二区大全| 性插视频无遮挡在线免费观看| 久久久久免费精品人妻一区二区| 国产一区二区亚洲精品在线观看| 亚洲三级黄色毛片| 丰满人妻一区二区三区视频av| 别揉我奶头 嗯啊视频| 最新中文字幕久久久久| 国产一级毛片在线| 国产真实伦视频高清在线观看| 久久99热6这里只有精品| 亚洲激情五月婷婷啪啪| 久99久视频精品免费| 国产精品久久久久久久电影| 18禁裸乳无遮挡免费网站照片| 国产伦一二天堂av在线观看| 淫秽高清视频在线观看| 久久久精品免费免费高清| 2018国产大陆天天弄谢| 免费观看精品视频网站| 日韩欧美三级三区| 午夜久久久久精精品| 99久久中文字幕三级久久日本| 国产久久久一区二区三区| 免费播放大片免费观看视频在线观看| 午夜精品国产一区二区电影 | 精品国产一区二区三区久久久樱花 | 国产精品国产三级国产专区5o| 精品人妻偷拍中文字幕| 成人av在线播放网站| 1000部很黄的大片| 久久久久网色| 国产免费一级a男人的天堂| 插阴视频在线观看视频| 免费观看av网站的网址| 丰满少妇做爰视频| h日本视频在线播放| 精品久久久久久久末码| 成年版毛片免费区| 久久午夜福利片| 国产av码专区亚洲av| 午夜福利视频1000在线观看| 美女脱内裤让男人舔精品视频| 国语对白做爰xxxⅹ性视频网站| 在线a可以看的网站| 成人无遮挡网站| 在线a可以看的网站| 一本久久精品| 人人妻人人澡人人爽人人夜夜 | 免费黄频网站在线观看国产| 最近最新中文字幕免费大全7| 99热这里只有是精品50| 国产av不卡久久| 精品一区二区三卡| 激情五月婷婷亚洲| 在线播放无遮挡| 一级二级三级毛片免费看| 搞女人的毛片| 观看美女的网站| 色综合色国产| 97热精品久久久久久| 国产有黄有色有爽视频| 久久久色成人| 亚洲精品视频女| 亚洲一区高清亚洲精品| 看非洲黑人一级黄片| 熟妇人妻不卡中文字幕| 久久久成人免费电影| 国产高清三级在线| 一级a做视频免费观看| 成人一区二区视频在线观看| 久久久精品94久久精品| 国产伦一二天堂av在线观看| 两个人视频免费观看高清| 夫妻性生交免费视频一级片| 综合色丁香网| 国产精品.久久久| 亚洲国产最新在线播放| 日本黄大片高清| 日韩 亚洲 欧美在线| 国产亚洲5aaaaa淫片| 亚洲精品中文字幕在线视频 | 亚洲真实伦在线观看| 色视频www国产| 看非洲黑人一级黄片| 国产乱人偷精品视频| av又黄又爽大尺度在线免费看| 青春草视频在线免费观看| 国国产精品蜜臀av免费| 国产精品不卡视频一区二区| 69人妻影院| 波野结衣二区三区在线| 一本久久精品| 久久久久久九九精品二区国产| 午夜激情欧美在线| 亚洲国产精品sss在线观看| 欧美高清性xxxxhd video| 美女国产视频在线观看| 欧美一级a爱片免费观看看| 亚洲国产欧美人成| 亚洲,欧美,日韩| 久久韩国三级中文字幕| 亚洲电影在线观看av| 熟女人妻精品中文字幕| 久久99精品国语久久久| 女的被弄到高潮叫床怎么办| www.色视频.com| 大又大粗又爽又黄少妇毛片口| av一本久久久久| 特级一级黄色大片| 国产av国产精品国产| 亚洲成人av在线免费| 亚洲精品日本国产第一区| 亚洲精品久久久久久婷婷小说| 亚洲一区高清亚洲精品| 又大又黄又爽视频免费| 亚洲在线自拍视频| av一本久久久久| 国内精品一区二区在线观看| 国模一区二区三区四区视频| 亚洲av日韩在线播放| 日韩一区二区三区影片| 少妇丰满av| 精品久久久噜噜| 亚洲最大成人av| 国产欧美另类精品又又久久亚洲欧美| 日韩欧美一区视频在线观看 |