GIS based surface hydrological modelling in identification of groundwater recharge zones

Digital elevation model (DEM) is a storehouse of a variety of hydrological information along with terrain characteristics. In recent years, automatic extraction of drainage network from DEM with the help of Geographical Information System (GIS) has become possible and is now being practised the world over for hydrological studies. In the present study, a comparative analysis of the drainage network derived from DEM and drainage extracted from surveyed topographical maps has been carried out. A comparative analysis based on nearest neighbour analysis on an intersection theme of two drainage networks showed that there is clustering (randomness<1) existing at places which show potential groundwater recharge zones. The suitable groundwater recharge zones identified in the drainage comparative analysis also show good correlation with the suitable recharge maps derived from remote sensing and GIS based procedure. In this study, two different watersheds (a) Dwarkeshwar in Bankura district, West Bengal, India, and (b) Kethan in Vidisha districts of Madhya Pradesh, India have been taken to analyse for identification of suitable groundwater recharge zones. The drainage comparative analysis approach developed and tested successfully in the present study is quick and reliable for the identification of suitable groundwater recharge zones particularly in a hard rock terrain.     

Integrated remote sensing and GIS for groundwater exploration and identification of artificial recharge sites

IRS-LISS-II data along with other data sets have been utilized to extract information on the hydrogeomorphic features of a hard rock terrain in the Sironj area of Vidisha district of Madhya Pradesh, India. The study exhibits reservoir induced artificial groundwater recharge downstream of surface water reservoirs. IRS-LISS-II data have been supported by information derived from DEM, drainage and groundwater data analysed in a GIS framework. The present study attempts to select suitable sites for groundwater recharge in a hard rock area through recharge basins or reservoirs, using an integrated approach of remote sensing and GIS. Criteria for GIS analysis have been defined on the basis of groundwater conditions in the area and appropriate weightage has been assigned to each information layer according to its relative contribution towards the desired output. The integrated study helps in designing a suitable groundwater management plan for a hard rock terrain.     

Groundwater potential modelling in a soft rock area using a GIS

A Geographical Information System (GIS) integration tool is proposed to demarcate the groundwater potential zone in a soft rock area using seven hydrogeologic themes: lithology, geomorphology, soil, net recharge, drainage density, slope and surface water bodies. Except for net recharge and slope, the other five themes are derived from remote sensing data. IRS-1B LISS-II data was used for a 631 km² area in Midnapur District, West Bengal, India. While slope was calculated using topographic sheets, net recharge was obtained from annual water table fluctuation data. Each feature of all the thematic maps was evaluated according to its relative importance in the prediction of groundwater potential. The evolved GIS-based model of the study area was found to be in strong agreement with available borehole and pumping test data.     

Typology of oases in northern Oman based on Landsat and SRTM imagery and geological survey data

In the desert country of Oman, available water resources are scarce and scattered. In most locations where water can be accessed, this resource is harnessed by oases planted to date palm (Phoenix dactylifera L.) and other crops. So far, little is known about the site-specific conditions determining the existence, size and type of these oases. Remote sensing and image processing techniques were used to locate oases, to characterize the sites according to their topographic, hydrologic and geologic characteristics and to develop a typology of oases in northern Oman.To derive oasis positions, we calculated the Normalized Difference Vegetation Index (NDVI) of Landsat images covering all of northern Oman, subtracted a regional average NDVI, averaged the resulting grid over 3 × 3 pixels and extracted the brightest of five classes determined by a natural breaks algorithm. A buffer of six pixels was added to the oases and the vegetated area as determined by the NDVI was summarized for these polygons. The oasis detection procedure was validated using Google Earth Pro®. Topographic information was derived from data of the Shuttle Radar Topography Mission (SRTM), complemented by digitized Russian military maps, from which mean elevations and elevation range above the oases within a buffer of 2 km were extracted.Water contributing upslope area and distance to streams with catchments of 10 km² and 100 km² were derived from the same elevation model. All geologic formations of northern Oman were assigned to one of 7 groups and tested for influence on vegetation surrounding them. Four such geologic settings were identified and described by categorical variables. All input parameters were used to define oasis types based on cluster analysis.Our algorithm detected 2663 oases in northern Oman, of which 2428 had vegetated areas of more than 0.4 ha, the minimum size for reliable detection. The oases were subdivided into six groups. ‘Plain Oases’ (49% of all oases) lie mostly in the plains east and west of the mountains, and are fed by groundwater flow in Quaternary sediments. ‘Foothill Oases’ (46%) are scattered over the foothills, where they draw their water from groundwater flow that is channeled by rock formations. ‘Mountain Oases’ (3%) and ‘Kawr Oases’ (0.5%) lie in the mountains, close to an unconform boundary between limestones and confining rocks. ‘Drainage Oases’ (0.3%) are the largest oases in northern Oman. They lie close to a drainage channel, which drains the entire area west of the mountains. Finally, ‘Urban Oases’ (1.7%) consist of parks and sporting facilities, which do not lie in conclusive hydrologic settings.     

Modeling surface water-groundwater interaction in arid and semi-arid regions with intensive agriculture

In semi-arid and arid areas with intensive agriculture, surface water-groundwater (SW-GW) interaction and agricultural water use are two critical and closely interrelated hydrological processes. However, the impact of agricultural water use on the hydrologic cycle has been rarely explored by integrated SW-GW modeling, especially in large basins. This study coupled the Storm Water Management Model (SWMM), which is able to simulate highly engineered flow systems, with the Coupled Ground-Water and Surface-Water Flow Model (GSFLOW). The new model was applied to study the hydrologic cycle of the Zhangye Basin, northwest China, a typical arid to semi-arid area with significant irrigation. After the successful calibration, the model produced a holistic view of the hydrological cycle impact by the agricultural water use, and generated insights into the spatial and temporal patterns of the SW-GW interaction in the study area. Different water resources management scenarios were also evaluated via the modeling. The results showed that if the irrigation demand continuous to increase, the current management strategy would lead to acceleration of the groundwater depletion, and therefore introduce ecological problems to this basin. Overall, this study demonstrated the applicability of the new model and its value to the water resources management in arid and semi-arid areas.     

Delineation of groundwater recharge sites using integrated remote sensing and GIS in Jammu district,India

With the increasing demands for water due to increasing population, urbanization and agricultural expansion, groundwater resources are gaining much attention, particularly in the Kandi region of Jammu district, which faces acute shortages of drinking water throughout the year. Groundwater development programmes need a large volume of data from various sources. This study used integrated remote sensing and geographic information system (GIS) techniques to provide an appropriate platform for convergent analysis of multidisciplinary data and decision making for artificial recharge to groundwater. Thematic maps were constructed using merged Linear Imaging Self Scanner (LISS)‐III and Panchromatic (PAN) remote sensing data and aquifer parameter thematic layers were prepared from conventional field data. The thematic layers of the aquifer parameters were integrated and a map showing the potential zones for artificial recharge to groundwater was generated. By superimposing the drainage network map over this artificial recharge zone map, and also considering the terrain conditions for artificial recharge, suitable sites for replenishing groundwater in the study area were identified.     

HydroTrend v.3.0: A climate-driven hydrological transport model that simulates discharge and sediment load leaving a river system

HydroTrend v.3.0 is a climate-driven hydrological water balance and transport model that simulates water discharge and sediment load at a river outlet, by incorporating drainage basin properties (river networks, hypsometry, relief, reservoirs) together with biophysical parameters (temperature, precipitation, evapo-transpiration, and glacier characteristics). HydroTrend generates daily discharge values through: snow accumulation and melt, glacier growth and ablation, surface runoff, and groundwater evaporation, retention and recharge. The long-term sediment load is predicted either by the ART-QRT module based on drainage area, discharge, relief, and temperature, or the BQART module that also incorporates basin-average lithology and anthropogenic influences on soil erosion. Sediment trapping efficiency of reservoirs is based on reservoir location in the river network and its volume that determines the residence time of water within the reservoir. Glacial influence is based on the extent of ice cover, equilibrium altitude, and freezing line mobility. HydroTrend v.3.0 captures the inter- and intra-annual variability of sediment flux by using either high-resolution climate observations or a stochastic climate generator for simulations over longer geological intervals. A distributary channel module simulates the flow conditions and transport capacity across a multiple deltaic channel system. Simulations of the Metauro and the Po rivers, in Italy, are used as case studies to demonstrate the applicability of the new model.     

针对华北地区地下水河湖生态补水成效的卫星遥感动态监测

为评估华北地区地下水超采治理河湖生态补水成效,基于现有国产卫星遥感影像覆盖能力,收集 2020 年华北地区 22 条(个)河湖流域卫星遥感动态监测影像数据,以相关水利基础数据为依据,构建一套完整的针对华北地区地下水河湖生态补水成效的水体遥感监测方案,将影像进行正射、融合、裁剪等预处理后,运用水体指数和深度学习 2 种方法对预处理后的遥感影像进行解译分析,提取河湖流域水面面积和有水河段长度,并结合河湖生态补水量进行验证,分析年内变化规律。监测结果表明：2020 年 7—12 月期间华北地区补水河湖水面面积和有水河段长度减少趋势减缓,并出现增加趋势。通过生态补水有利于缓解超采区水面面积减少趋势,验证通过统筹多种水源、调节时空布局,开展河湖回补地下水的方案是确有成效的。     

Comparison of 1D models of water flow in unsaturated soils

Understanding the interaction between soil, vegetation and atmosphere processes and groundwater dynamics is of paramount importance in water resources planning and management in many practical applications. Hydrological models of complex water resource systems need to include a number of components and should therefore seek a balance between capturing all relevant processes and maintaining data requirement and computing time at an affordable level. Water transfer through the unsaturated zone is a key hydrological process connecting atmosphere, surface water and groundwater. The paper focuses on the analysis of the modelling approaches that are generally used to describe vertical water transfer through unsaturated soil in hydrological models of water resource systems: a physically based approach, using numerical solutions of Richards' equation, and two conceptual models, based on reservoir cascade schemes, are compared. The analysis focuses on the soil water content in the top soil (first meter) and on the outflow from the profile (i.e. recharge to the aquifer). Results show that the water contents simulated by the mechanistic and conceptual models are in good agreement, unless the capillary fringe reaches the top soil (i.e. groundwater table very close to the soil surface). The ability of conceptual models to capture the daily recharge dynamics is generally rather poor, especially when fine textured soils and thick profiles are considered; a better agreement is found when recharge is accumulated over longer time periods (e.g. months). Improvements can be achieved by allowing the number of reservoirs in cascade to vary with changing profile depth, although scientifically sound rules for fixing the number of reservoirs need to be established.     

A simulation model of hydrology and nutrient dynamics in wetlands

A simulation model of the hydrology and nutrient dynamics in wetlands typical of central and north Florida was developed to predict parameters of water depth, recharge, and surface outflow as well as concentrations of total phosphorus, and three nitrogen species. The hydrological portion of the model predicts hydroperiod and depth of inundation for any elevation, and can be used to establish characteristic hydroperiod for vegetation and associations of species. The nutrient portion of the model can be used to predict water quality within, and quality of surface water outflow from natural wetlands, constructed wetlands, and wetlands receiving treated effluent or storm drainage. Programmed in BASIC for simulation on desktop microcomputers, the model is interactive requiring data input such as wetland type, discharge rate, and the concentrations of nutrients in surface water inflow.     

Satellite-based estimates of groundwater storage variations in large drainage basins with extensive floodplains

This study presents monthly estimates of groundwater anomalies in a large river basin dominated by extensive floodplains, the Negro River Basin, based on the synergistic analysis using multisatellite observations and hydrological models. For the period 2003-2004, changes in water stored in the aquifer is isolated from the total water storage measured by GRACE by removing contributions of both the surface reservoir, derived from satellite imagery and radar altimetry, and the root zone reservoir simulated by WGHM and LaD hydrological models. The groundwater anomalies show a realistic spatial pattern compared with the hydrogeological map of the basin, and similar temporal variations to local in situ groundwater observations and altimetry-derived level height measurements. Results highlight the potential of combining multiple satellite techniques with hydrological modeling to estimate the evolution of groundwater storage.     

祁连山区植被净初级生产力的空间变化特征分析

基于MODIS数据分析了2000~2010年祁连山区植被净初级生产力(Net Primary Productivity,NPP)的空间变化特征。结果显示:祁连山区植被NPP并不高,多年平均植被NPP仅为121.95gC/(m2·a),自东向西植被NPP逐渐减少。不同植被类型其NPP具有明显差异,大体上为:常绿阔叶林平原草地常绿针叶林典型草地农田高寒草甸草地荒漠草地落叶针叶林。祁连山区植被NPP变化在区域间也存在差异。植被NPP呈增长趋势的地区主要分布在青海年南山、拉脊山、达坂山和青海湖及其西侧,约占47.30%;乌鞘岭东部及以东的地区(约占1.97%)植被NPP呈减少趋势。降水是祁连山区植被NPP变化的主要因素,气温对植被NPP的影响并不明显,不合理的人类活动可能是造成部分区域植被NPP减少的重要原因。     

Analysis of the spatiotemporal changes in terrestrial water storage anomaly and impacting factors over the typical mountains in China

Based on the terrestrial water storage anomaly (TWSA) from Gravity Recovery and Climate Experiment (GRACE) and Global Land Data Assimilation System, Tropical Rainfall Measuring Mission products, groundwater level data, and teleconnection indexes, combined with the Mann–Kendall test, the spatiotemporal distribution of TWSA and its potential drivers during 2002–2015 were explored over the mountains areas located in the transitional zone between the non-monsoon and monsoon areas in China. The major conclusions can be seen the follows: (1) as for the time series of TWSA from GRACE, the increasing trend with the rate of 0.15 mm month^?1 was investigated over Karst area, and the decreasing trends with the rate of ?0.61 and ?0.32 mm month^?1 were exhibited over Taihang Mountains and Hengduan Mountains; (2) the significant decreasing trend (p < 0.05) of TWSA from GRACE was found over Taihang Mountains and the west of Hengduan Mountains, and the significant increasing trend (p < 0.05) was explored over the north of Karst area; (3) precipitation played an important role in the changes of TWSA over Hengduan Mountains and Karst area, while the groundwater played a dominant role in the changes of TWSA over Taihang Mountains. The anthropogenic contributions of ?92.9 ± 22.3, 13.47 ± 3.2, and 61.9 ± 14.85 mm yr^?1 to TWS were detected over the Taihang Mountains, Hengduan Mountains, and Karst area, respectively. In addition, El Niño-Southern Oscillation (ENSO) impacted on the changes of TWSA deeply over these three regions, especially the Hengduan Mountains and Karst area during 2002–2015.     

Monitoring of urban growth of a desert city through remote sensing: Al-Ain,UAE, between 1976 and 2000

The objective of this article is to investigate the development of Al Ain city, in the United Arab Emirates (UAE), between 1976 and 2000, with particular reference to the space–time relationship. Al Ain is the fastest changing city in the Arabian Peninsula. It has gone from a desert oasis to a thriving modern city in just over 30 years. Maps, colour aerial photographs, satellite imagery, Global Positioning System (GPS), and Geographical Information System (GIS) were used as an aid for understanding the development of the city. Change and development in the city is evident from comparison of old maps, aerial photographs, and satellite imagery taken during 1976, 1978, 1984, 1994, 1998 and 2000. The city was found to have a tendency for major expansion in the direction of the west and south-west. Expansion in any direction was found to be governed by the availability of utilities (water, electricity), economic activities along roads (agriculture, industry), geographical constraints (valleys, sand dunes, mountains), and legal factors (boundary with Sultanate of Oman, planning and institutional rules). Many cities around the world are developed at the cost of agricultural areas, which are the main source of food. For example, in Tempe, Arizona between 1970 and 1979 and in Cairo. However, in Al Ain the research concludes that the development is based on conservation of agricultural areas (oases) and reclamation of the desert. Revenue from oil is a significant drive for this development, but even more important is the determination of the UAE government to proceed with the development.     

卫星重力监测全球地下水储量变化及其特征

地下水储量是水资源管理和陆地表面过程与水循环研究的一个重要参数。然而,由于传统观测技术成本高和空间分辨率低等局限性，很难建立一个全球连续的综合地下水监测网，因此监测全球高时空分辨率的地下水储量及其变化仍是当前的一个挑战。2002年发射的低低卫—卫跟踪“重力恢复与气候试验”(GRACE)重力卫星为高分辨率地监测全球地下水储量及其变化，提供了一种新的可能手段。利用2002年8月~2011年2月的GRACE观测数据估计近10 a的月间隔全球陆地水总储存量，扣除了GLDAS水文模型（全球陆地数据同化系统）中的地表水、冰雪和生物水，得到全球地下水储量时间序列，并分析其季节性和长期变化及其特征。研究结果表明:GRACE探测到全球地下水储量具有明显的季节性变化，例如在南美洲的亚马逊河流域和亚洲中南部的周年振幅达到50 mm，而在澳大利亚南部和非洲北部的周年振幅只有10 mm左右。另外全球地下水储量具有明显的长期变化，如南美洲亚马逊河流域由于洪水造成地下水储量以6 mm/a的速率增加，拉普拉塔地区由于干旱造成地下水储量以7.5 mm/a的速率减少;中国新疆吐鲁番盆地地区的地下水储量以3.1 mm/a的速率减少,中国华北地区的地下水储量以4.8 mm/a的速率下降。     

Simulating the influences of groundwater on regional geomorphology using a distributed,dynamic, landscape evolution modelling platform

A dynamic landscape evolution modelling platform (CLiDE) is presented that allows a variety of Earth system interactions to be explored under differing environmental forcing factors. Representation of distributed surface and subsurface hydrology within CLiDE is suited to simulation at sub-annual to centennial time-scales. In this study the hydrological components of CLiDE are evaluated against analytical solutions and recorded datasets. The impact of differing groundwater regimes on sediment discharge is examined for a simple, idealised catchment, Sediment discharge is found to be a function of the evolving catchment morphology. Application of CLiDE to the upper Eden Valley catchment, UK, suggests the addition of baseflow-return from groundwater into the fluvial system modifies the total catchment sediment discharge and the spatio-temporal distribution of sediment fluxes during storm events. The occurrence of a storm following a period of appreciable antecedent rainfall is found to increase simulated sediment fluxes.     

Application of remote sensing and GIS for the demarcation of groundwater potential zones of a river basin in Kerala,southwest coast of India

An integrated hydrogeological investigation has been made to delineate the groundwater‐potential zones of the Muvattupuzha river basin, Kerala, along the southwest coast of India. The basin is characterized by charnockites and gneisses of Archean age covering more than 80% of the area and the remaining by Pleistocene laterites and Miocene formation. The basin receives high rainfall, measuring 3100 mm/year. However, acute water shortage occurs during the premonsoon season and hence, a number of dug wells are made to tap the groundwater. Seasonal rainfall during NE and SW monsoons is the major source of groundwater recharge. Further, hydrogeomorphology, geology, fracture systems and the slope of the terrain also play a significant role on the movement and behaviour of the groundwater of this basin. The integration of conventional and remote sensing data has been made through geographic information system (GIS) and it is found that about 50% of the area can be identified as very good or good potential zones, whereas the remaining area falls under moderate and poor categories. Most of the Muvattupuzha sub‐basin and the western part of the Kothamangalam and Kaliyar sub‐basins are classified as good groundwater‐potential zones, although the eastern upstream part of the basin has poor groundwater potential.     

Seasonal and interannual variability of chlorophyll-a in the Gulf of Oman compared to the open Arabian Sea regions

Field sampling, remote sensing and modelling were employed to understand the seasonal and interannual changes of chlorophyll-a concentrations in the Gulf of Oman in comparison to open sea regions. In these regions, maximal chlorophyll concentrations were reported during the summer monsoon (with peaks in June and August), while in the Gulf of Oman, the chlorophyll maximum was observed during the winter monsoon (February–March). From 1997 through to 2008, the interannual variability in chlorophyll-a concentrations in the Gulf of Oman has not exhibited pronounced trends and neither have the other two (oceanic) regions in the western Arabian Sea. However, an increase of the annual variation in chlorophyll concentrations over the years was noticed. The diatom biomass decreased two-fold from 1997 to 2007. Nitrate concentration and mixed-layer depth also declined. In comparison to the seasonal blooms driven in the Gulf of Oman by the dinoflagellate Noctiluca scintillans, the year 2008 was markedly different. The summer bloom was shifted to September; it was gradually extended in time and formed by the other species. An applicability of the concept of ecosystem regime shift is discussed.     

Observation of hydrological features with Nimbus-7 37 GHz data,applied to South America

Abstract

The microwave polarization difference temperature (MPDT) prepared from 37 GHz Scanning Multifrequency Microwave Radiometer (SMMR) data from the Nimbus-7 satellite allows a unique vision of hydrological features, especially of humid areas. From the series of monthly images from 1979 to 1985 the major hydrological features of four major river basins of South America are briefly examined. These include rivers of the Amazon, La Plata, Orinoco and Sao Francisco basins, wetlands in the La Plata and Amazon basins and floods in the La Plata basin. Many hydrological features appear much as they do on conventional maps. An interesting perspective can be derived from the ways in which they differ from conventional maps.     

Investigating attitudes towards the use of mobile learning in higher education

Mobile learning (M-learning) has become an important educational technology component in higher education. M-learning makes it possible for students to learn, collaborate, and share ideas among each other with the aid of internet and technology development. However, M-learning acceptance by learners and educators is critical to the employments of M-learning systems. Attitudes towards M-learning technology is an important factor that helps in determining whether or not learners and educators are ready to use M-learning. Such attitudes will serve to identify strengths and weaknesses and facilitate the development of the technology infrastructure. This paper aims at exploring students and educators' attitudes towards the use of M-learning in higher educational universities within Oman and UAE; two neighboring countries in the Arab Gulf region. To serve this purpose, two survey questionnaires were conducted: one for students and another for educators. The participants of this study are 383 students and 54 instructors from five universities. Different factors have been examined to test where there is a significant difference among students and educators' attitudes towards the use of M-learning, such as gender, age, country, level of study, smartphone ownership, major in terms of students and age, country, academic rank, academic experience and smartphone ownership in terms of educators. Findings revealed significant differences among the students’ attitudes towards M-learning with regard to their smartphone ownership, country and age. Furthermore, results indicated that M-learning can be one of the promising pedagogical technologies to be employed in the higher educational environments within the Arab Gulf countries.