Quantitatively analyze the impact of land use/land cover change on annual runoff decrease

Annual runoff in Luanhe river basin was detected a downward trend and caused water crisis in Tianjin, China. To quantify the decreased runoff volume, Mann–Kendall test and Pettitt test were employed to check whether there existed significant trend and change points for annual rainfall and runoff time series in Panjiakou reservoir basin and 8 sub-watersheds. It was found that the annual runoff time series had a significant downward trend at 5 % confidence level, and the change point was at 1979 in Panjiakou reservoir watershed. Then double mass curve of annual rainfall and annual runoff was plotted, and two lines were fitted before and after 1979, respectively. Based on this method, the comprehensive effects of land use/land cover change on annual runoff were estimated. To further quantify the contributions of each main factor to annual runoff decrease, water stored in check dams and social water use in different periods were surveyed first. And then multi-linear regression was used to develop the relations between annual runoff and the driven factors. Water area decrease was identified to be the main factor contributing to annual runoff reduction. The results in this study can provide valuable information for water resources planners and policy makers.     

气候变化、土地利用/覆被变化及CO2浓度升高对滦河流域径流的影响

在构建分布式水文模型与生物地球化学模型的耦合模型（DTVGM-CASACNP）及应用元胞自动机-马尔科夫（CA-Markov）土地利用预测模型基础上,以滦河流域为例分析气候变化、土地利用/覆被变化（LUCC）及CO₂浓度升高对径流的影响。研究结果表明: DTVGM-CASACNP耦合模型以及CA-Markov模型在滦河流域均具有较好的适用性;气候变化与土地利用/植被覆盖变化对滦河流域径流的影响较CO₂浓度升高的影响程度大;未来不同情景下滦河流域2020—2049年径流呈减小趋势,大部分情景下年径流较基准年减少,与非汛期相比,滦河流域未来汛期径流对不同情景更敏感,总体上在汛期径流相对基准年减少,而在非汛期径流相对基准年增加。     

土地利用变化对海河流域典型区域的径流影响

为研究海河流域径流对土地利用变化的响应,以阜平流域、匡门口流域和界河铺流域为研究区,利用1970—2011年的水文气象资料,分析了不同土地利用的时空转移特征,然后结合SWAT(Soil and Water Assessment Tool)模型,设置4种土地利用情景,评价了土地利用变化对径流的影响。结果表明:模型能够较好地模拟全年及汛期月流量过程;多年径流量呈下降趋势,20世纪80年代到90年代中期呈波动性变化;不同的土地利用类型在时空上的转化呈现可逆性,主要是林地增加,草地减少,耕地略有增加;林地的增加和草地的减少会降低汛期径流量以及最大月径流量;汛期径流系数随着林地面积的增加而减小。合理地规划土地利用格局,对控制流域水文事件具有重要意义。     

Assessment of land use land cover change impact on hydrological regime of a basin

The sustainability of water resources mainly depends on planning and management of land use; a small change in it may affect water yield largely, as both are linked through relevant hydrological processes, explicitly. However, human activities, especially a significant increase in population, in-migration and accelerated socio-economic activities, are constantly modifying the land use and land cover (LULC) pattern. The impact of such changes in LULC on the hydrological regime of a basin is of widespread concern and a great challenge to the water resource engineers. While studying these impacts, the issue that prevails is the selection of a hydrological model that may be able to accommodate spatial and temporal dynamics of the basin with higher accuracy. Therefore, in the present study, the capabilities of variable infiltration capacity hydrological model to hydrologically simulate the basin under varying LULC scenarios have been investigated. For the present analysis, the Pennar River Basin, Andhra Pradesh, which falls under a water scarce region in India, has been chosen. The water balance components such as runoff potential, evapotranspiration (ET) and baseflow of Pennar Basin have been simulated under different LULC scenarios to study the impact of change on hydrological regime of a basin. Majorly, increase in built-up (13.94% approx.) and decrease in deciduous forest cover (2.44%) are the significant changes observed in the basin during the last three decades. It was found that the impact of LULC change on hydrology is balancing out at basin scale (considering the entire basin, while routing the runoff at the basin outlet). Therefore, an analysis on spatial variation in each of the water balance components considered in the study was done at grid scale. It was observed that the impact of LULC is considerable spatially at grid level, and the maximum increase of 265 mm (1985–2005) and the decrease of 48 mm (1985–1995) in runoff generation at grid were estimated. On the contrary, ET component showed the maximum increase of 400 and decrease of 570 mm under different LULC change scenario. Similarly, in the base flow parameter, an increase of 70 mm and the decrease of 100 mm were observed. It was noticed that the upper basin is showing an increasing trend in almost all hydrological components as compared to the lower basin. Based on this basin scale study, it was concluded that change in the land cover alters the hydrology; however, it needs to be studied at finer spatial scale rather than the entire basin as a whole. The information like the spatial variation in hydrological components may be very useful for local authority and decision-makers to plan mitigation strategies accordingly.     

Assessment of soil erosion in a tropical mountain river basin of the southern Western Ghats,India using RUSLE and GIS

Revised Universal Soil Loss Equation(RUSLE) model coupled with transport limited sediment delivery(TLSD) function was used to predict the longtime average annual soil loss, and to identify the critical erosion-/deposition-prone areas in a tropical mountain river basin, viz., Muthirapuzha River Basin(MRB; area=271.75 km~2), in the southern Western Ghats, India. Mean gross soil erosion in MRB is 14.36 t ha~(-1) yr~(-1), whereas mean net soil erosion(i.e., gross erosion-deposition) is only 3.60 t ha~(-1) yr~(-1)(i.e., roughly 25% of the gross erosion). Majority of the basin area(~86%) experiences only slight erosion(5 t ha~(-1) yr~(-1)), and nearly 3% of the area functions as depositional environment for the eroded sediments(e.g., the terraces of stream reaches, the gentle plains as well as the foot slopes of the plateau scarps and the terrain with concordant summits). Although mean gross soil erosion rates in the natural vegetation belts are relatively higher, compared to agriculture, settlement/built-up areas and tea plantation, the sediment transport efficiency in agricultural areas and tea plantation is significantly high,reflecting the role of human activities on accelerated soil erosion. In MRB, on a mean basis, 0.42 t of soil organic carbon(SOC) content is being eroded per hectare annually, and SOC loss from the 4th order subbasins shows considerable differences, mainly due to the spatial variability in the gross soil erosion rates among the sub-basins. The quantitative results, on soil erosion and deposition, modelled using RUSLE and TLSD, are expected to be beneficial while formulating comprehensive land management strategies for reducing the extent of soil degradation in tropical mountain river basins.     

Effects of land use/cover change on regional land surface temperatures: severe warming from drying Toshka lakes,the Western Desert of Egypt

Natural Hazards - Toshka depression in the Western Desert of Egypt witnessed big floods in late 1990s from the Nile River behind the High Dam, where many lakes were formed. By the year 2003, the...     

长江黄河源区覆被变化下降水的产流产沙效应研究

在长江和黄河源区的左冒西孔曲和纳通河、垮热洼尔玛河流域的不同植被覆盖下建立了天然径流观测场,利用观测天然降水和人工模拟降水,初步研究了江河源区不同植被覆盖下降水的产流产沙效应。结果表明,长江黄河源区的3个小流域内,在典型高寒草甸草地30°坡面上,退化较为严重的30%覆盖度以下的场地内,地表径流产出量明显大于覆盖度较好的95%、92%和68%场地,同时产沙量显著高于这3个场地,其平均单次降水形成的泥沙量是这三种盖度的2~4倍,由此造成地表侵蚀量平均为这3种盖度的3~10倍。通过对几次典型的降水形态的分析,在长江黄河源区高寒草甸草地的坡面上,不但降水量影响着产流产沙量,降水形态也影响着产流产沙量,降雨仍是引起水土流失的主要降水形态,在降水量相同的条件下,降雪可比降雨和雨加雪增加产流量2.1~3.5倍,可比降雨减少泥沙侵蚀45.4%~80.3%。人工模拟结果表明:对于覆盖度为5%和30%的强度退化草地,次降水量在3.5 mm时,就形成了较为明显的径流和产沙效应,当次降雨量达到7 mm,降雨持续时间15 min,5 m2场地内就会形成1 400 mL以上的径流量;在地表土壤含水量(FDR测0~5 cm平均含水量为36.7%)较高的情况下,次降雨量达4mm,降雨强度超过0.4 mm/min,在5 m2场地内历时5 min就能形成1 060 mL的地表径流,每100 mL径流中含泥沙高达1.6 g。这一试验结果在长江黄河源区3个不同的河源小流域是一致的。     

Springs in a headwater basin in the Deccan Trap country of the Western Ghats, India

Available literature reveals that little work has been done on the origin of springs in a basaltic terrain. Close examination of such springs in about 2,000 km² of the upper Koyna River basin in the Deccan Trap country of the Western Ghats (hills), India, reveals that their origins are dependent on the lithologic character of different basaltic flow units and the existing physiography. Although rainfall, its seasonality and areas of recharge, play vital roles in the recharge of these springs, their yields are also controlled by lithological variations and hydraulic characteristics of their source-aquifers. Chemical concentrations of these springs are heavily dependent on the lithological compositions of the source-aquifers and the residence time of groundwater in these aquifers. Currently, basaltic springs are classified with those issuing from other terrains. However, because the emergence of groundwater in the form of springs is largely controlled by the lithology and the resulting water-bearing properties of the formations, a new classification scheme is proposed that classifies the springs on the basis of their source-aquifers. While tapping springs for drinking/irrigation purposes, it must be remembered that they also sustain thousands of other life forms vital to a balanced ecosystem. Changes in the uses of these springs may also affect other human communities downstream. Therefore, before developing spring flow, a trade-off must be made considering local needs and downstream users. Emphasizing only local human needs may lead to severe intercommunity conflict and negative environmental consequences. Electronic Publication     

气候与土地利用变化对涟水流域径流的影响

以涟水流域为研究对象,选用1990年、2000年、2010年三期土地利用数据资料,将1985-2014年30 a气象条件相应划分为1985-1994年、1995-2004年、2005-2014年三段气象背景时期,并组合细分为7种模拟情景,应用SWAT分布式水文模型模拟不同情景下的径流量,探讨气候和土地利用变化对流域径流的影响。利用PSO粒子群优化算法,以克林效率系数KGE为目标函数,通过湘乡站实测径流数据校准模型参数。运用p-factor、r-factor评价模拟的不确定性,采用相关系数R²、纳什效率系数NS和偏差百分比PBIAS评价模型模拟效果,评价结果表明不同土地利用情景下,校准期和验证期的模拟效果均达到可信程度,模拟的不确定性较小。组合情景间模拟分析结果表明,1985-2014年30 a间,气候变化使涟水流域径流不断减少,土地利用变化使径流有所增加,年径流深总体呈现下降趋势。气候变化对涟水流域径流变化的影响贡献率在逐渐上升,从71.4%上升到了86.3%。土地利用变化对径流变化的影响贡献率则相应下降,从28.6%降低至13.7%。因此,在气候变化背景下,科学管理流域水资源还需要充分考虑流域土地资源空间配置结构和利用方式。     

Assessment of the effects of climate and land cover changes on river discharge and sediment yield,and an adaptive spatial planning in the Jakarta region

In Jakarta, climate change has been detected through rising air temperatures, increased intensity of rainfall in the wet season, and sea level rise. The coupling of such changes with local anthropogenic driven modifications in the environmental setting could contribute to an increased probability of flooding, due to increase in both extreme river discharge and sedimentation (as a result of erosion in the watersheds above Jakarta and as indicated by sediment yield in the downstream area). In order to respond to the observed and projected changes in river discharge and sediment yield, and their secondary impacts, adaptation strategies are required. A possible adaptation strategy is through policy making in the field of spatial planning. For example, in Indonesia, presidential regulation number 54 year 2008 (Peraturan Presiden Nomor 54 Tahun 2008—Perpres 54/2008) was issued as a reference for the implementation of water and soil conservation. This paper assesses the impact of climate and land cover change on river discharge and sediment yield, as well as the effects of Perpres 54/2008 on that river discharge and sediment yield. The spatial water balance model Spatial Tools for River Basins and Environmental and Analysis of Management Option was used for the runoff computations, whilst the Spatial Decision Assistance of Watershed Sedimentation model was used to simulate erosion, Sediment Delivery Ratio, and sediment yield. The computation period is from January 1901 to December 2005, at the scale of the following watersheds: Ciujung, Cisadane, Ciliwung, and Citarum. During the twentieth century, computed average discharge in the downstream area (near Jakarta) increased between 2.5 and 35 m³/s/month, and sediment yield increased between 1 × 10³ and 42 × 10³ tons/year. These changes were caused by changes in both land cover and climate, with the former playing a stronger role. Based on a computation under a theoretical full implementation of the spatial plan proposed by Perpres 54/2008, river discharge would decrease by up to 5 % in the Ciliwung watershed and 26 % in the Cisadane watershed. The implementation of Perpres 54/2008 could also decrease the sediment yield, by up to 61 and 22 % in the Ciliwung and Cisadane watersheds, respectively. These findings show that the implementation of the spatial plan of Perpres 54/2008 could significantly improve watershed response to runoff and erosion. This study may serve as a tool for assessing the reduction in climate change impacts and evaluating the role of spatial planning for adaptation strategies.     

Changing land use/land cover patterns and growing human population in Wular catchment of Kashmir Valley,India

GeoJournal - The profound increase in human activities and the degrading scenario in fragile ecosystems of the western Himalayas like that of Wular Lake have highlighted the need to analyze the...     

环境变化对黄河中游汾河径流情势的影响研究

20世纪70年代后我国许多河流的径流量呈下降的趋势.在这些趋势变化中,如何区分人类活动及气候变化的影响是当前流域水文研究的热点和难点.提出了区分人类活动和气候变化影响的分析思路以及定量计算方法.介绍了SIMHYD概念性降水径流模型,并应用黄河中游汾河流域"天然"时期的水文、气象资料率定了模型参数,通过水文模拟还原了人类活动影响期间的天然径流量,进而分析了汾河流域径流情势的变化原因.结果表明:SIMHYD降水径流模型对汾河流域天然月径流过程具有良好的模拟效果;就1970-1999年的平均状况而言,气候因素和人类活动对径流的影响量分别占径流减少总量的35.9%和4.1%,人类活动是汾河流域径流减少的主要因素.     

Modelling soil moisture under different land covers in a sub-humid environment of Western Ghats,India

The objective of this study is to apply and test a simple parametric water balance model for prediction of soil moisture regime in the presence of vegetation. The intention was to evaluate the differences in model parameterization and performance when applied to small watersheds under three different types of land covers (Acacia, degraded forest and natural forest). The watersheds selected for this purpose are located in the sub-humid climate within the Western Ghats, Karnataka, India. Model calibration and validation were performed using a dataset comprising depth-averaged soil moisture content measurements made at weekly time steps from October 2004 to December 2008. In addition to this, a sensitivity analysis was carried out with respect to the water-holding capacity of the soils with the aim of explaining the suitability and adaptation of exotic vegetation types under the prevailing climatic conditions. Results indicated reasonably good performance of the model in simulating the pattern and magnitude of weekly average soil moisture content in 150 cm deep soil layer under all three land covers. This study demonstrates that a simple, robust and parametrically parsimonious model is capable of simulating the temporal dynamics of soil moisture content under distinctly different land covers. Also, results of sensitivity analysis revealed that exotic plant species such as Acacia have adapted themselves effectively to the local climate.     

Effects on runoff caused by changes in land cover in a Brazilian southeast basin: evaluation by HEC-HMS and HEC-GEOHMS

The Southeast Region of Brazil has undergone major changes in land cover, especially after the eighteenth century. It is currently the most populous region of the country, highly urbanized, with a high degree of industrial and agricultural development. Extensive areas of native vegetation have been replaced by pastures, crops and urban areas, which have increased runoff, causing environmental, economic and social problems related to flooding. The objective of this study was to analyze effects of land cover changes in a basin with rural and urban characteristics on the flow of its main river. Hydrological data, orbital images, soils and topographical maps were used for this purpose. Based on the land cover maps for the years of 1989, 2001 and 2015, and on the hydrological modeling performed using the Hec-HMS 4.1 software, scenarios were simulated and showed that the land cover changes in this basin significantly affect the flow behavior of the main river. The simulated runoff was calibrated using the data observed in the field during 2001, and validation was performed using data from 1989. After the calibration and validation processes, a scenario was simulated where the rainiest month of the whole series measured by the rainfall station (during December 1989) acted on the land cover of 2015. There was an increase in pasture areas and impermeable spaces in the basin, which caused a decrease in infiltration and an increase in surface runoff, and also an increase in the flow peaks and a reduction in the time of concentration. The hydrological modeling was satisfactory, since the uncertainties related to the simulation were low.     

Effects of land use/cover change on atmospheric humidity in three urban agglomerations in the Yangtze River Economic Belt,China

Natural Hazards - Land use/cover change (LUCC) affects regional climate not only through its direct changes of land surface properties, but also through its further modifications of...     

Seasonal variation in major ion chemistry of a tropical mountain river,the southern Western Ghats,Kerala, India

A comprehensive and systematic study to understand various geochemical processes as well as process drivers controlling the water quality and patterns of the hydrochemical composition of river water in Muthirapuzha River Basin, MRB (a major tributary of Periyar, the longest river in Kerala, India), was carried out during various seasons, such as monsoon, post-monsoon and pre-monsoon of 2007–2008, based on the data collected at 15 monitoring stations (i.e., 15 × 3 = 45 samples). Ca²⁺ and Mg²⁺ dominate the cations, while Cl^? followed by HCO₃ ^? dominates the anions. In general, major ion chemistry of MRB is jointly controlled by weathering of silicate and carbonate rocks, which is confirmed by relatively larger Ca²⁺ + Mg²⁺/Na⁺ + K⁺ ratios as well as Ca²⁺/Na⁺ vs. Mg²⁺/Na⁺ and Ca²⁺/Na⁺ vs. HCO₃ ^?/Na⁺ scatter plots. The relationship between Cl^? and Na⁺ implies stronger contributions of anthropogenic activities modifying the hydrochemical composition, irrespective of seasons. The water types emerged from this study are transitional waters or waters that changed their chemical character by mixing with waters of geochemically different ionic signatures. However, various ionic ratios, hydrochemical plots and graphical diagrams suggest seasonality over the hydrochemical composition, which is solely controlled by the rainfall pattern. Relatively higher pCO₂ indicates the disequilibrium existing in natural waterbodies vis-à-vis the atmosphere, which is an outcome of both the contribution of groundwater to stream discharge and anthropogenic activities. Hence, continuous monitoring of hydrochemical composition of mountain rivers is essential in the context of climate change, which has serious implications on tropical mountain fluvial-hydro systems.     

Drainage morphometry of upper Vaigai river sub-basin, Western Ghats, South India using remote sensing and GIS

The study area is a one of the sub-basin of Vaigai River basin in the Theni and Madurai districts, Western Ghats of Tamil Nadu. The Vaigai sub-basin extends approximately over 849 km² and it has been sub-divided into 48 watersheds. It lies between 09°30′00″ and 10°00′00″N latitudes and 77°15′10″ and 77°45′00″ E longitudes in the western part of Tamil Nadu, India. It originates at an altitude of 1661m in the Western Ghats of Tamil Nadu in Theni district. The drainage pattern of these watersheds are delineated using geo-coded Indian remote sensing satellite (IRS) ID, linear image self-scanning (LISS) III of geo-coded false colour composites (FCC), generated from the bands 2, 3 and 4 on 1:50,000 scale in the present study. The Survey of India (SOI) toposheets 58G/5, 58 G/6, 58G/9 and 58G/10 on a scale of 1:50,000 scale was used as a base for the delineation of watershed. In the present study, the satellite remote sensing data has been used for updation of drainages and the updated drainages have been used for morphometric analysis. The morphometric parameters were divided in three categories: basic parameters, derived parameters and shape parameters. The data in the first category includes area, perimeter, basin length, stream order, stream length, maximum and minimum heights and slope. Those of the second category are bifurcation ratio, stream length ratio, RHO coefficient, stream frequency, drainage density, and drainage texture, constant of channel maintenance, basin relief and relief ratio. The shape parameters are elongation ratio, circularity index and form factor. The morphometric parameters are computed using ESRI’s ArcGIS package. Drainage density ranges from 1.10 to 4.88 km/km² suggesting very coarse to fine drainage texture. Drainage frequency varies from 1.45 to 14.70 which is low to very high. The bifurcation ratio ranges from 0.55 to 4.37. The low values of bifurcation ratios and very low values of drainage densities indicate that the drainage has not been affected by structural disturbances and also that the area is covered under dense vegetation cover. Elongation ratio ranges from 0.11 to 0.57. Drainage texture has the minimum of 1.63 and maximum of 11.44 suggesting that the drainage texture is coarse to fine. It is concluded that remote sensing and GIS have been proved to be efficient tools in drainage delineation and updation. In the present study these updated drainages have been used for the morphometric analysis.     

Use of SWAT to determine the effects of climate and land use changes on streamflow and sediment concentration in the Purna River basin,India

A semi-distributed, physically based, basin-scale Soil and Water Assessment Tool (SWAT) model was developed to determine the key factors that influence streamflow and sediment concentration in Purna river basin in India and to determine the potential impacts of future climate and land use changes on these factors. A SWAT domain with a Geographical Information System (GIS) was utilized for simulating and determining monthly streamflow and sediment concentration for the period 1980–2005 with a calibration period of 1980–1994 and validation period of 1995 to 2005. Additionally, a sequential uncertainty fitting (SUFI-2) method within SWAT-CUP was used for calibration and validation purpose. The overall performance of the SWAT model was assessed using the coefficient of determination (R²) and Nash–Sutcliffe efficiency parameter (E_NS) for both calibration and validation. For the calibration period, the R² and E_NS values were determined to be 0.91 and 0.91, respectively. For the validation period, the R² and E_NS were determined to be 0.83 and 0.82, respectively. The model performed equally well with observed sediment data in the basin, with the R² and E_NS determined to be 0.80 and 0.75 for the calibration period and 0.75 and 0.65 for the validation, respectively. The projected precipitation and temperature show an increasing trend compared to the baseline condition. The study indicates that SWAT is capable of simulating long-term hydrological processes in the Purna river basin.     

土地利用变化对流域生态需水的影响分析

人类对流域生态系统的干预,导致季节性淹没区减少,天然湿地丧失,生态环境的恶化和生物多样性锐减,土地利用方式发生了剧烈变化。以流域整体性理论、物种多样性理论、物种耐性理论和景观生态学理论为基础,分析了土地利用方式对生态需水的影响。结果表明,河岸天然植被生态系统通过削减洪峰、增补枯水和截留污染物的作用,来影响流域的水量分配和水质改善,使流域受水分不足威胁的程度降低,即在更大的时间与空间尺度上,保证了流域对生态水的需求。因此,为了流域生态系统的可持续发展,应采取保护湿地、河溪森林植被、水陆交错带等合理的土地利用方式。