Groundwater scenario under climate change and anthropogenic stress in Ladakh Himalaya, India

In the Himalayan regions of Jammu, Kashmir, and Ladakh, groundwater is a potential freshwater source of the sustained water supply (Andermann et al. 2012; Müller et al. 2020; Illien et al. 2021). The groundwater has been preserved for centuries through several measures (e.g. Changnon et al. 1988; Dolma et al. 2015a) such as judicious use of water (Angchok & Singh 2006; Tundup et al. 2017), traditional water conservation (Nüsser et al. 2012), and sanitation mechanisms (Dawa et al. 2009). Additionally, the impact of climate change on the resources was generally disregarded (e.g. Barrett & Bosak 2018). However, significant changes have occurred in the groundwater resources during the past two decades (BORDA 2019; CGWB 2022). Ladakh region has been strategically very important between India, China, and Pakistan. The region received huge attention, particularly after 1974 due to political disputes between the countries. A huge population expansion, rapid urbanization, rural-to-urban migration, impetus in the tourism sector, rapid economic growth, change of the living standard and lifestyle of the people, and unmanaged development have been witnessed during recent decades (Goodall 2004; Pellicardi 2010; BORDA 2019; Dame et al. 2019). These processes increased the per-capita water demand and put a huge pressure on the water resources of Ladakh which imbalanced the demand–supply relation. The rising water requirements of households, hotels, and guesthouses are now met through a network of dug wells and extensive groundwater pumping stations (Arghyam 2013; Yangchan et al. 2019). The growing agricultural activities in Ladakh (Dolker 2018) also increased the water demand and groundwater abstraction. About 7% of the pumped groundwater is used for irrigation and 93% for domestic and industrial purposes in the Leh district (CGWB 2020). Moreover, the significant changes in climate have also impacted the water resources of the region (Nüsser et al. 2019; Mir 2021). High inter/intra-annual climate variability, rising temperature, and low/erratic precipitation are depleting the cryosphere and water resources (Chevuturi et al. 2018; Yangchan et al. 2019; Nüsser et al. 2019; Müller et al. 2020). Climate change and human activities have also affected the recharge, replenishment, and groundwater volume in this ecologically sensitive region (e.g. Earman & Dettinger 2011). The problems are severe, particularly in the developing urban mountain towns of Leh and Kargil (Müller et al. 2020).

In general, the drastic increase in groundwater draft has created a state of depletion as compared to the situation some 15–20 years before when no bore well drilling machines were found in the region (BORDA 2019). The district-wise groundwater extraction/recharge map (Figure 1(b)) of Jammu, Kashmir, and Ladakh also shows variable values. The index varies from 0% in the western Pir Panjal region of Jammu to about 66% in the major towns of Jammu, Srinagar, and Leh (CGWB 2022). These high values indicate that more than 66% of the annual replenished resource is abstracted in these towns from the aquifers. The continued withdrawal at this rate and less recharge due to the change of climate have affected the water levels, and spring discharge, and degraded the water quality in many parts of Leh (The Asian Age 2009; Balamurugan et al. 2016; Yangchan et al. 2019). People report cases of water crises, water disputes, and pollution problems, indicating water unavailability and insecurity (The Asian Age 2009; Chattopadhyay et al. 2019). Unscientific groundwater exploitation is another major concern in the area (e.g. Müller et al. 2020). Improper sewage systems and direct disposal of domestic waste into the soak pits or improperly constructed septic tanks are common (Dolma et al. 2020; Müller et al. 2020). This directly pollutes the groundwater, especially in densely populated areas (Gondhalekar et al. 2015). Recharge is also less due to semi-arid climate and low precipitation, which leads to slow replenishment of contaminated groundwater. Groundwater is constrained by complex hydrogeology, physiography, meteorology, high evaporative demand, and permeable regolith. Nonetheless, groundwater is also highly vulnerable to climate change (e.g. Ososkova et al. 2000; Negi et al. 2009; Xu et al. 2009; Barthel et al. 2012; World Bank 2012; Kulkarni et al. 2002; Wunsch et al. 2022), natural hazards, and underdeveloped infrastructure (Ziegler et al. 2016). As per the IPCC (2019) report ‘groundwater has been impacted by climate change worldwide but due to the lack of observations, the extent of these changes are not clear’. Continued degradation will affect the water supply, food security, economic prosperity, and sustainable development of the region (Manivannan et al. 2017; Reach Ladakh Bulletin 2018; Third Pole 2018; Gleeson et al. 2020).

The Union Territory (UT) of Ladakh, situated in the north of India (Figure 1), has very significant importance in terms of geopolitics, climate, cryosphere, and hydrology between Tibet, Pakistan, and China. The Indian part of Ladakh has a total area of 59,146 km² distributed between Leh and Kargil districts covering an area of 45,110 and 14,036 km², respectively. Leh, falling within toposheet 52F/12, is the second-largest district in India. The district has 8 tehsils, 16 blocks, and 112 villages, and Leh town, a Class – III urban area of 19 km² with a population of 30,870 and major tourist facilities. The total population of Ladakh, including army personnel and tourists, is 274,289 (Census of India 2011). Nearly, 133,487 people live in Leh and 140,802 in the Kargil district. The current (2020) population of UT is about 290,492 and that of Leh is about 152,175. Population density is 3 persons/km² and the majority of the people live in low-lying valleys. About 66% of the population is rural and only 34% is urban.

The cold desert Ladakh (Kumar et al. 2012) is arid to semi-arid and falls in the tropical and subtropical (BWk type) of Köppen climate classification (Muller 2012). Leh constitutes 87.4% of the total cold arid region of India (Wani et al. 2011). The regional climate of Ladakh (Singh et al. 1995; Mölg et al. 2014; Madhura et al. 2015; Lone et al. 2017; Rowan 2017) is generally controlled by these wind systems;

• 1.

  Western Disturbances (WD) from the Atlantic Ocean, Mediterranean, Black, and Caspian Seas,

• 2.

  The Indian Summer Monsoons (ISM) from the Bay of Bengal and the Arabian Sea,

• 3.

  The Tibetan anticyclone, and

• 4.

  The fluctuating Inter-Tropical Conversion Zone

Extremely rugged topography with high structural hills and amphitheatre valleys with plains called Thangs, alluvial plains, piedmont (curvilinear ridges of loose material at the foothills), and glacial-fluvial quaternary landforms characterize the geomorphology. The Karakoram, Ladakh, Zanskar, and Greater Himalaya ranges demarcate the topography. The relief of the Ladakh Range varies between 7,742 m asl at Saltoro Kangri to 2,550 m asl at the Indus River and 3,524 m at Leh (Supplementary Figure S1(a)). The low-lying plain areas including the Leh Plain, More Plain, and Hanle Plain (Hanle River marshes) are densely populated. The Leh or Ganglas catchment is one of the major valleys with an area of 175 km² in the area. The relief is highly variable. The low-lying plains and valleys, cultivated for dryland crops, have 0°–30° slope (Supplementary Figure S1(b)).

The Indus, Shyok, and Nubra are the major transboundary river systems of the Upper Indus Basin of the Ladakh region (Cheema & Qamar 2019). The Indus (Supplementary Figure S1(a)) flows for about 422 km in Leh, which is 87% of its total flow length in India. It has an annual flow of about 243 km³ making it one of the world's largest rivers. The river has historical significance and is the lifeline of the region. It originates from a perennial spring (Senge Khabab) in Tibet and collects several snow- and glacier-fed rivers downstream. Discharge is low in winter and high between July to September. The perennial Nubra River from Siachen Glacier flows 80 km and joins the Indus. Shyok River from Rimo Glacier joins the Nubra R. at about 290 km downstream near Tirit and Disket. The Zanskar R. brings more discharge than the Indus from Zanskar and confluences with it at Nimmo.

The Indus R. is structurally controlled and follows the NW-SE trending Karakoram Fault and Indus Tsangpo Suture Zone (ITSZ). Indus Valley in some places is 2–3 km wide with a braided pattern, e.g. Chumathang and Leh. It transports huge sediments mainly due to highly weathered catchments, loose quaternary sediments, high density of structures, and high (up to 7) stream order (Clift et al. 2002; Sharma et al. 2017; Tiwari et al. 2021). It also transports huge plastic waste into the Arabian Sea (Schmidt et al. 2017).

The Ladakh region forms an essential component of the 3rd Pole (Hindu Kush Himalaya) hosting a large number of glaciers covering nearly 33,000 km² (Dyurgerov & Meier 1997; Mukhopadhyay & Dutta 2010; Mir et al. 2018). More than 1,800 glaciers spread to nearly 997 km² are present in the region (Lone et al. 2021). About 90% of them occur between 3,000 and 5,200 m asl and 80% have an average area of 0.75 km² (Frey et al. 2014; Mir 2021). Siachen glacier spreads to ∼700 km² (Frey et al. 2014; Nüsser et al. 2019). The glaciers of the Himalayan-Karakoram ranges have an area of 40,775 km² and ice volumes between 2,955 and 4,737 km³ (Frey et al. 2014). More than 50% of the total glaciers of India are located in the Ladakh and Zanskar ranges which include ∼5,000 glaciers of ∼3,187 km² area and an ice volume of ∼816 km³ (Koul 2018). The cryosphere sustains the river flow (Bookhagen & Burbank 2010; Immerzeel et al. 2013; Kaser et al. 2010), groundwater recharge (Jeelani et al. 2021; Lone et al. 2021), domestic and irrigation needs of ∼1.5 billion people in the surrounding countries of India, Pakistan, Nepal, Bhutan, and China (Immerzeel et al. 2010; Engel et al. 2016; Jeelani & Deshpande 2017; Mir 2021; Tiwari et al. 2021), and maintains the ecosystems (Barry & Gan 2011; Immerzeel et al. 2020; Mir et al. 2023). The melt water contributes ∼50% to the river flow mainly in its upper catchments (Xu et al. 2009). Part of the glacier melt percolates through fractures and other lineaments into the aquifers. A very high percolation rate reduces stream flow, for example by up to 90% in Zanskar (Angchok & Singh 2006). Pangong Lake, Tsomoriri Lake, and hot springs of Panamic, Chumathang, and Puga are other important water bodies in the area. Climate change and high consumption have reduced surface water flow and several streams dry up in summer, thereby affecting the downstream hydrology, hydrogeology, and cultivation. To cope with this, artificial glaciers are also developed around higher elevations in the area (Nüsser et al. 2019).

The land-use and land-cover (LU-LC) map of Leh was obtained from the Environmental Systems Research Institute (ESRI 2021) with a spatial resolution of 10 m (https://www.arcgis.com/ accessed on 11-08-2021). The analysis showed that about 77% of the district is a hilly terrain occupied by snow/glaciers and is unfavorable for living or cultivation (Supplementary Figure S2(a), inset). The Leh valley is 80% rocky area, 8% agriculture, and 7% built-up (Balamurugan et al. 2016). About 5% is the low-lying valley covered by unconsolidated sediments that are used for build-up and cultivation. The soil is immature, composed of boulders, sand, silt, and clay with high permeability (CGWB 2022). The soils are poor in fertility, gravely, sandy, sandy loam, silty, clay loam to clayey with pH of 7.4 to 9.6 (Wani et al. 2011). Coarse sandy loam soil is more widespread than silty clay and clay loam. Soil is poor in most of the ingredients. Major soil composition is sand 55.4–80.7%, silt 12.6–19.1%, and clay 6.44–10.9% (Kumar et al. 2021). In the Zanskar valley, the soil contains 5.4% coarse matter, 58% sand, 20% silt, 15% clay and 1.6% organic matter. The soil possesses a low water-holding capacity of 13 to 17% (Raina & Koul 2011). Organic carbon in the soils of Leh varies between 0.07–1.41% (Sharma et al. 2006). Soil cover is generally very thin (a few cm to < meter) and stores very low moisture (Wani et al. 2011). The moisture content is also lost quickly due to high permeability and evaporation processes (Raina & Koul 2011; CGWB 2022).

Natural vegetation is scanty, including xerophytic shrubs and small trees (Alnus, Betula) (Paudyal et al. 2016). Cultivable land is <1% of the total area and is grown for crops such as wheat, grim (naked barley), mustard, lentils, and vegetables. Agriculture, an allied economic activity, supports the livelihoods of a small population between April and October. In recent years, new crops and fruits have been cultivated. About 90% of farmers use surface water (gravity flow) and 10% pump groundwater (CGWB 2022). Irrigation is done at intervals of 10–12 days. Highly permeable soil makes cropping even more difficult. A few protected national parks, and wildlife sanctuaries are also present (David 2010).

The geological setup showing four major thrust or tectonomorphic zones (Henderson et al. 2010) is shaped by the collision tectonics between the Eurasian and Indian plates over the past 45 million years (Thakur & Misra 1984; Thakur & Rawat 1992). Four prominent thrust zones from north to south demarcate the major rock formations of Ladakh. Karakoram strike-slip fault bounds Karakoram Plutonic Complex (KPC). The Shyok Suture Zone (SSZ) is a relic marginal basin between KPC and Ladakh Batholith (LB). The ITSZ includes the relics of past oceanic lithosphere consisting of the Shergol melange, Nidarophiolitic complex, and volcanic (Dras formation, Khardung volcanic, and Ladakh Batholiths). The ITSZ demarcates the Indian continent and the Asian continent (Searle & Owen 1999; Clift et al. 2002). The Zanskar Suture Zone (ZSZ) bounds the Zanskar crystalline complex of oceanic origin.

The LB and the Indus Group of rocks largely define the geology of Leh (Supplementary Figure S2(b)). The Batholith consists of rocks of tonalite, granodiorite intrusives, and granite with mafic enclaves (Thakur 1981). The Zanskar Formation is composed of forearc-basin meta-sedimentary rocks of the Paleozoic to Paleocene age (Mathur et al. 2009). The rocks of the Indus Group/Formation consisting of conglomerate, sandstone, siltstone, and shale are of Paleocene to Early Miocene age (Robertson 2000; Henderson et al. 2010; Singh et al. 2015). Choksti Thrust along which the Zanskar Range was uplifted during a major uplift period in the Miocene also demarcates contact between two rock formations (Sinclair & Jaffey 2001). Major gorges occur in this thrust zone due to tectonic movements of ∼17.8 mm/year (Jade et al. 2004). Toward the north and northeast of the area, the volcanic and plutonic rocks including the Khardung Formation, KPC, Shyok Formation, and Pangong Metamorphic Complex are present (Singh et al. 2015). Well-preserved glacial moraines, fluvio-glacial, and fan deposits are widespread in the area (Phartiyal et al. 2009). The terraces and foothills between the hills form a landform locally called Thang such as Taru Thang where Taru village is located. These are composed of thick beds of boulders, cobbles, sand, silt, and clay deposits. Quaternary lacustrine deposits are also present (Phartiyal et al. 2009). The region is prone to neotectonic activities along fault/thrust zones (Kotlia et al. 1997; Clift et al. 2008).

However, it is pertinent to note that recharge, discharge, and other inflow–outflow processes of the aquifer system are little understood in the area. In general, the hydrogeology is controlled by varied topography, type and thickness of aquifers, and the thickness/nature of the regolith (Jeelani et al. 2018a, 2018b; Joshi et al. 2018; Kong et al. 2019; CGWB 2020). In granite aquifers, the vertical structure depends on the weathering profile where regolith is generally less than a few centimeters in high slopes to more than 50 m in the valley bottoms. Recharge is controlled by microclimate and catchment characteristics (Schmidt & Nüsser 2017; Beck et al. 2018; Chevuturi et al. 2018; Müller et al. 2020). Generally, recharge is about 83% from melt water (44% from glaciers, 39% from snow) and only 17% from rainwater (Lone et al. 2021). The rainfall infiltration factor in the alluvial and moraine deposits is 20% (CGWB 2009). Considering annual precipitation of 105 and 84 mm as evapotranspiration in Leh, the average recharge rate can be accounted for as high as 21 mm per year. The recharge-worthy zone is merely 2.8% in the area (CGWB 2009). Focused recharge through weathered and fractured zones occurs between 3,100–3,500 m asl (Lone et al. 2021). The density of lineaments, fractures, joints, and drainage affects groundwater flow. The focused infiltration of glacial melt water also occurs through the loose and unconsolidated moraine and glacial deposits around high elevations (Figure 4(c)). Probably, the glacier-fed streams may also be supplementing the infiltration to groundwater resources in the area. Little recharge also occurs through irrigation where the return-flow factor could be 15–25% (CGWB 2009). Low slope, high lineament and drainage density, and porous regolith increase groundwater potential in low-elevations, which become promising sites for groundwater development (GWD), augmentation, and protection (Balamurugan et al. 2016). Springs occur at the contact of geological formations as well as along fractures, faults, and thrust zones (CGWB 2009). In the Leh Valley, about 86 documented springs discharge 0.0015–0.29 m³/min in summers and less in winters (Balamurugan et al. 2016). The total groundwater discharge in the Leh district is about 5.8 million cubic meters (MCM) i.e. 11.3% of the annual recharge volume (Supplementary Table S1). Very high hydraulic gradient causes drying of wells/springs in the recharge zones mainly in the dry season. Bore well failure is common because of loose regolith. Moreover, several hot springs near Panamic and Chumathang yield deep hot water (temperature 73–85 °C) at a rate of 0.009–0.02 m³/s. But, till now, no major and systematic hydrogeological study has been taken up to characterize the aquifer system, resouce estimation and understand the groundwater behavior in the area.

A number of studies suggest an increasing trend in the temperature and erratic behavior of precipitation over the Ladakh region in recent years. In this study, Climatic Research Unit (CRU) time-series (TS) v-4.05 half-degree gridded monthly temperature data of the Ladakh region was used to understand the trends in temperature change and precipitation climatic variables (source: https://crudata.uea.ac.uk/cru/data/hrg/cru_ts_4.05/) (Harris et al. 2020). The climate scenario (TERI Climate Tool, source: http://tct.teriin.org/ClimatePortal/V1/ClimateAnalysis.aspx accessed 15-05-2023) was employed to analyze the future trends in temperature change and precipitation data. The changes in climatic variables are discussed briefly in the following.

The analysis of the CRU dataset indicates that mean annual temperature exhibits large variation and significant rising trends (e.g., decadal) during the last century from 1901 to 2020 (Supplementary Figure S3(a)). A minimum temperature of –1.20 °C was observed in 1967, whereas 2009 recorded a temperature of 3.23 °C. The average annual temperature increased during 1901–1950 and then decreased during 1950–2000. But, during the recent two decades (2000 till 2020), it showed large variability and a significantly rising trend (Supplementary Figure S3(a)). Overall, temperature is rising significantly from 1900 to 2020 at a rate of 0.0014 °C/year to a confidence level of 95% as the Z statistics are greater than 1.95 level (Z = 6.2; P = 0.01). Earlier studies (e.g. Bhutiyani et al. 2007; Dash et al. 2007; Bhutiyani et al. 2010; Mir et al. 2015a, 2015b, 2017; Chevuturi et al. 2018; Lone et al. 2019) also indicated a rise in temperature by about 0.2 °C (rate 0.0013 °C/year) in the past 10–20 years (Table 3). In the Drass region, the mean annual temperature has increased by 0.6 °C from 1900 to 2019 (Romshoo et al. 2022). The mean monthly minimum and maximum temperatures have also increased significantly after 2000 AD in the region (Raina & Koul 2011; Tundup et al. 2016). Summers are warming at the rate of 0.006 °C/year and winters at the rate of 0.08 °C/year (Lone et al. 2019). Extreme temperature events are common (Archer & Fowler 2004). Temperature is predicted to rise further by 1 °C from the current temperature in the near future due to increasing greenhouse gases and aerosol emissions as well as land-use and land-cover changes in the area (Romshoo et al. 2022). The trend is comparable to global warming which has increased the temperature by 1.1 °C from 1850 to the present and affected the natural processes in every part of the world (IPCC 2023). Rising temperatures, increased precipitation variability, and changes in the pattern and direction of wind systems have strongly affected the local to regional climate (Schmidt & Nüsser 2017; Beck et al. 2018). However, the climate change studies are insufficient (Chevuturi et al. 2018) and generally refer to the regional values (e.g. average over the whole Ladakh; Shafiq et al. 2016) and small time periods of 10–20 years (see Table 3). Some studies are also based on low-resolution satellite and gridded data (e.g. Chevuturi et al. 2018; Kumar et al. 2018; Banerjee & Dimri 2019).

Contrarily to temperature rise, the precipitation shows large seasonal and annual variability in volume, time, and mode, especially during the last century in the Ladakh region (Chevuturi et al. 2018; Lone et al. 2019; Romshoo et al. 2022). Analysis of the CRU data (Harris et al. 2020) in this study revealed the highest annual precipitation of 323 mm in 1957 and 140.8 mm in 2009. A gentle declining pattern was found from 1901 to 1945 at a rate of ∼0.03 mm/year (e.g. Lone et al. 2019). Precipitation increased from 1945 to 1970 and after the 1970s it again declined (Supplementary Figure S3(b)). Some parts of Ladakh received more precipitation (Dash et al. 2007; Chevuturi et al. 2018) and higher rates of rainfall (Tundup et al. 2016). Summer rainfall has increased by 0.11 mm/year, whereas the spring and autumn precipitation increased by 0.21 and 0.09 mm/year, respectively. Machiwal et al. (2017) also indicate that the annual and summer rainfall is increasing at both Kargil and Leh. Ladakh also witnessed decreased winter snowfall at 0.18 mm/year, decreased winter duration, and more rainfall than snow (Chevuturi et al. 2018; Nüsser et al. 2019; Müller et al. 2020) and an increase in winter rain (Upadhyaya et al. 2023). Snow falls in late winter, i.e. late January and February (Lone et al. 2021). Dry days are increasing in number each year in the Ladakh region (Dimri & Dash 2012; Yangchan et al. 2019). Also, the higher temperature leads to the sublimation of the cryosphere thereby increasing the summer precipitation (Raina & Koul 2011). The mean annual RH has also decreased between 2000 and 2022 at a rate of 2% per year (Tundup et al. 2016). The decreasing humidity indicates that future precipitation will have a lower probability of occurrence in Ladakh. The intensity and the frequency of extreme events have increased, thereby resulting in frequent flash floods, glacier lake outburst floods, landslides, and other related disasters (Nandargi & Dhar 2011; Thayyen et al. 2013). Overall, as a result of a warming climate, a decline and change in the form of precipitation from solid to liquid is observed in the region (Mir et al. 2018). Table 3 summarizes the analysis of overall climate change in Leh, Ladakh during the past century.

The future climate projections over the Leh (e.g. TERI Climate Tool, http://tct.teriin.org/ClimatePortal/V1/ClimateAnalysis.aspx accessed on 10-05-2022) indicate that the mean temperature is expected to increase from current −2 °C to +1 °C by 2050 with an increase of 0.06° per year at optimal Representative Concentration Pathway (RCP) of 8.5. The precipitation is not changing too much (slope of trend = 0.003% change per year) but its pattern will be extremely variable in space and time. Few studies (Chevuturi et al. 2018) suggest that the future predictions of climate trends are somewhat ambiguous due to lack of sufficient data. For example, Kumar et al. (2018) indicate a falling trend in maximum temperature over the region. Therefore, a sufficient and suitable dataset is required to conduct further studies to analyze the climate data trends and to simulate its impacts on the water resources of the region.

Economic prosperity also encouraged rapid urbanization in recent decades. The average density of population in the urban area of Leh Municipality Center, Spituk, and Choglamsar Census Towns is 2,100 persons/km². The spread of urban centers to villages caused population growth from 2,895 in 1911 to 50,671 in 2020, i.e. addition of 438 persons/year (Figure 5(a)). Dramatic and unethical construction activities also increased the built-up area by 20% from 1969 to 2017 and by about 75% in the last 10 years around major towns at the cost of suitable land classes (Wani et al. 2009; Dar et al. 2017; Dame et al. 2019). New residential houses, commercial buildings, guesthouses, and hotels are constructed swiftly and indiscriminately. On average, 30 new guesthouses are registered each year. Between 2000 and 2018, the cumulative number of hotels and guesthouses grew linearly with R² = 0.97 (Figure 5(b) and inset in 5(b)). Almost 75% of the families run a hotel or a guesthouse and have 24 h of water supply. The number of vehicles also increased 4-fold from about 4,007 in 1994 to nearly 16,300 in 2007 (Figure 5(b)). Atmospheric Greenhouse Gases; GHG (CO₂, NO_x, CH₄), black carbon, and particulate matter increased from 2011 to 2020 by about 39% (Romshoo et al. 2022). Furthermore, it is reported that the semi-arid climate and vegetation-free barren land do limit the CO₂ sequestration that exacerbates the warming trend (Zeb et al. 2020; Thakur et al. 2021).

The terrestrial water resources such as cryosphere and surface water bodies in the Himalayas have been significantly impacted due to the ongoing climate change and anthropogenic activities (Bhutiyani et al. 2007; Farinotti et al. 2015; Mir et al. 2013, 2014, 2017; Rowan 2017; Mir & Majeed 2018; Abdullah et al. 2020; Ali et al. 2021; Mir 2021). Glaciers have lost about 40% of area and 196 km³ of volume, which is equivalent to a sea level rise of up to 1.4 mm, particularly after the Little Ice Age (400–700 years ago) (Lee et al. 2021). About 13.4 km³ of glacier area was lost per year during 1962–2004 (Dyurgerov & Meier 2005; Rodell et al. 2009). Glacial thickness has decreased between 0.25–0.5 m annually and even more since 2000 onward (Maurer et al. 2019).

Glaciers have also been impacted in Ladakh due to climate variability. About 657 glaciers of the Ladakh Range have decreased in area by about 13–20% in 25 years between 1991 and 2014 (Chudley et al. 2017). Similarly, glacier volume has reduced by 12–17% between 1971 and 2019 (Mehta et al. 2023). About 90 glaciers in the Leh and Khardung regions have lost 12.5% (2.7 km²) of their area at a rate of 160 m²/year from 2000 to 2017 (Mir 2021). Romshoo et al. (2022) observed that glacial cover in the Drass region has reduced by 0.3 km² per year from 2000 to 2020. Similarly, Machoi Glacier of Ladakh has decreased by 29% in the 50-year period from 1972 to 2019 (Rashid et al. 2021). Glaciers, which are small, clean, and close to highways, are retreating faster due to the impact created by anthropogenic activities (Romshoo et al. 2022). The GHGs have increased temperature, glacier melting, and air pollution during the last few decades (Hock et al. 2019; Romshoo et al. 2022).

Glacier-melt water, a major source of stream water supply (Angchok & Singh 2006; Tundup et al. 2017), has decreased significantly during recent decades in the Leh region (Arghyam 2013; The Third Pole 2018; Dolma et al. 2020). The glacier-fed streams sometimes during summer seasons run totally dry due to loss of flow. The situation is further aggravated due to low precipitation or loss of source glaciers in the area (Sharma & Choudhury 2021). Glacier recession, early melting, and growing sublimation have changed the flow pattern, timing and thereby the availability of water supply (Eckhardt & Ulbrich 2003; Raina & Koul 2011; Lone et al. 2017). Furthermore, the additional losses due to evaporation have also increased by 8–15% in the area (Ososkova et al. 2000).

Similar impacts are observed on groundwater recharge and reserves of the area (Schmidt & Nüsser 2017; Sarkar et al. 2020; Mir 2021). Little recharge and excessive pumping (Chattopadhyay et al. 2019) have reduced natural discharge and dried springs and bore wells (Yangchan et al. 2019). The climate change impacts, and the subsequent loss of glaciers, permafrost, and permanent snowfields have further increased the water deficit. Recharge, constrained by steep and undulating topography, large runoff loss, and high evaporation, is substantially affected. As a result of this, there is an uncertainty about groundwater availability and sustainability (Sharma 2001; Barnett et al. 2005; WWF 2005; Immerzeel et al. 2010; Shekhar et al. 2010; Pritchard 2017; Yangchan et al. 2019; Tuladhar et al. 2023).

Studies in India (Roy & Balling 2004; Asoka et al. 2017) and elsewhere (Mileham et al. 2009; Owor et al. 2009; IPCC 2012) have attempted to incorporate the impacts of climate change on groundwater resources and sustainability studies. Overall, this relationship is poorly understood so far in the study region, which has proved hazardous to the sustainable development of groundwater. Therefore, detailed studies are required to understand this relationship elaborately in the region.

In Ladakh, the water demands have increased and imbalanced the supply–demand equation as compared to the pre-development period of 1974 (BORDA 2019; Bansal et al. 2023). Today a native person uses an average of ∼0.1 m³/day which is 5 times more than it was once (Narain 2002; Dawa et al. 2009). Floating populations further exacerbated water demands, particularly during summers. This caused water shortage, water insecurity, and rising water disputes, particularly in towns where water is supplied only for 4-h a day (Angchok & Singh 2006; The Asian Age 2009; Yangchan et al. 2019). Drinking water requirements are expected to rise by a factor of 5 by 2025 (Ladakh 2025 Vision Document 2005). The per-capita demand and water deficiency will also rise by more than 50% in the future (Balamurugan et al. 2016; Müller et al. 2020).

Tourist data and per-capita water requirements of 0.1–0.15 m³ per day of the region indicate that the water needs of Leh town are very high as compared to the water supply (Balamurugan et al. 2016; Müller et al. 2020). The Public Health and Engineering Department (PHE) supplies water through a network of pipelines. However, the demand is growing for the people who are personally pumping huge quantities of groundwater from the aquifers, which mostly remains undocumented. The current estimated groundwater draft in the Leh district for domestic and industrial needs is ∼7 MCM, i.e. 95% of the total abstraction (Supplementary Table S1). The domestic and industry needs are projected to rise by 33% of the current draft by 2025.

Irrigation is a major consumer of groundwater in India and utilizes more than 90% of total groundwater annually (Siebert et al. 2010; CGWB 2017a, 2017b, 2017c; Jain et al. 2019). Nationally, the net-irrigated area has increased from 18 to 48% and groundwater irrigated to net-irrigated area from 29 to 63% and increased groundwater draft in recent decades (CSO 2013; Siebert et al. 2013; Jain et al. 2019).

Rising agricultural land (Wani et al. 2011) is also a major concern in this barren desert of the Ladakh region. Each year more land is cultivated for trees, vegetation, food, and fruits due to warmer climates, various government policies, and to produce food to become self-sufficient (Wani et al. 2009; BORDA 2019). The rising warm periods also favor the cultivation of water-consuming crops in the area (Raina & Koul 2011; Cao & Roy 2020). The total sown area has increased by about 21 km² at a rate of 1.7 km²/year in the past 15 years (Table 4). Thus, higher irrigation water requirements stress the already limited groundwater because it is available independently, timely, and with no institutional restrictions. The current groundwater draft for irrigation is ∼0.41 MCM or 5.6% of the total draft (Supplementary Table S1). Leh Plain between Phyang Nala and Sabu Nala, where ∼0.1 MCM is pumped each year, is mainly affected and is categorized as a semi-critical zone based on the index of GWD (CGWB 2009, 2011). Additionally, rising hazards, such as flash floods, GLOFs, landslides, and creep (Khan et al. 2021) have also disturbed the ecosystem and affected recharge processes.

Extreme dependency on groundwater for irrigation and other uses in India has depleted the water table in ∼39% of the wells in the country and created severe groundwater crises in ∼64% of the total area of the country (CGWB 2017a, 2017b, 2017c; Jain et al. 2019). However, proper information is lacking about the water table and its variations in Ladakh. Analysis of the available data (CGWB 2009, 2017a, 2017b, 2017c, 2020; Balamurugan et al. 2016) indicates huge variability in the wells and water levels. The exploratory wells drilled by CGWB are 10 to 86 m deep. The water table shows significant variation in the topography and the aquifer types. The water level is generally shallower in valleys and low-lying plains. In Leh town, the water level is about 1.5 m bgl in the hilly Zorawar Fort and as deep as 43.4 m bgl at the ITBP site near Choglamsar (CGWB 2009). The water table in the moraine and granite aquifers is deeper (60–75 m bgl) than unconfined valley-fill deposits (25 m bgl). Wells at the times of drilling discharged between 870–1,303 m³/day (Supplementary Table S2). Transmissivity (T) ranges from 204 to 3,069 m²/day. The lack of information on wells and water levels highlights the need to understand the vertical picture of groundwater. Although there are numerous springs the monitoring of the flow and the chemistry has not been carried out elaborately in this area.

Specific Capacity calculated at the time of well drilling is an important indicator to measure the performance of aquifers (Driscoll 1986; Sterrett 2007). The maximum pumping rate (MPR) of a well is estimated by multiplying the SC value (Supplementary Table S2) with the maximum available drawdown, which can be equal to the total saturated thickness (b) of the aquifer. From this calculation, the MPR in the aquifers varies from 0.443 to 86.531 CM per minute with a mean of 9.339 CM per minute. This approximation provides the limits for the pumping rates of the wells in the area.

The SC is also used to track the performance of the wells and the aquifers using different performance indicators and time-series data of the SC. Studies have shown that wells lose SC with time due to various factors, mainly plugging of the pore spaces and the well construction material, mineral encrustations, turbulent flow, temperature changes, etc. (Driscoll 1986; Sterrett 2007). Turbulent flow and temperature fluctuate rapidly in the groundwater of the area and both will affect the aquifer systems over time and require proper measures like good monitoring, time-series data, etc. (e.g. Sterrett et al. 2008).

As per CGWB (2022) an average of 57 MCM of rainfall recharges the aquifers of the Leh district, out of which 6 MCM occurs as natural flow. The net annual groundwater available is ∼51 MCM. The current annual groundwater draft for irrigation, domestic, and industrial uses is ∼7 MCM. Only 0.4 MCM (∼0.7% of NGA) is pumped for irrigation and 6.87 MCM (∼10% of NGA) is pumped for domestic and industrial uses. The remaining untapped reserves have huge scope for sustainable development of the region. Rain/snow contributes mainly to groundwater recharge. Recharge from canals, ponds, etc. as calculated (CGWB 2020) is quite unreasonable in the area. The assessment reports provide no detailed account of groundwater data and aquifer-type water levels (CGWB 2020). Further, the estimates, using the conventional rainfall infiltration method, are based on several assumptions (CGWB 2017a, 2017b, 2017c) and have huge uncertainty (Chatterjee & Ray 2014). Supplementary Table S1 provides the summary of annual groundwater reserves estimated for many assessment periods. Using the same methodology, the values highly vary thereby, indicating its huge data gaps and limitations (Supplementary Table S1). For example, the recharge value is almost double in 2017 calculations and the net draft increased by almost 25 times in 2017 against 2009 values.

Assessment of the groundwater depletion rate in the region is also lacking. Nevertheless, literature values showed that depletion due to several factors is increasing. Two commonly used parameters, GWD, defined as groundwater draft as a percent of availability (CGWB 2022), and groundwater withdrawal as a percent of recharge, denote the stress on the reserves (Rodell et al. 2009). Both indices have increased in recent years, thereby signifying rising groundwater exploitation (Supplementary Table S1). The data show that GWD in Leh has risen from 1.34% in 2009 to 36.13% in 2020, a rise of about 26 times. The current withdrawal in terms of the percentage of recharge in the study area is about 66% (CGWB 2022) which is above the average range of 10–20% as estimated using NASA Gravity Recovery and Climate Experiment (GRACE) satellite data over India (Rodell et al. 2009). The results indicate that the increasing water demands and the decreasing recharge volume due to different factors in the region will increase the pumped volume further. In India, ∼16% of the assessment sites are already over-exploited with GWD >100% (CGWB 2017a, 2017b, 2017c).

The groundwater abstraction is very high in Leh town (Gondhalekar et al. 2013; BORDA 2019). About 90% of the water supply is sourced from groundwater (public, private, and government wells) and only 10% from surface water (springs and melt water). The Public Health Engineering (PHE) department pumps about 1.7 MCM/year of groundwater from shallow aquifers to deep (depth >30 m) tube wells and supplies through pipelines to the town households (Gondhalekar et al. 2013; BORDA 2019). Of this, 45% is pumped from Indus tube wells and 44% from PHE tube wells in Leh, while 12% is collected from the natural spring flow. In addition, shallower groundwater pumping (about 10 m deep) from personal wells is undocumented. About 74% of households in the town use piped water supplied by the PHE, 18% use hand pumps, and 8% use bore wells. Withdrawal is more in the spring season due to the limited water supply and late arrival of the melt water in the streams and aquifers (Dhiman 2019; Müller et al. 2020). Declined surface water and its pollution increase groundwater dependence and force people to drill personal wells (Müller et al. 2020). About 90% of the people of the area were using surface water from melt-off snow and glaciers some 15–20 years before the present. Now the shift is toward groundwater and currently more than 92% of people are dependent on it (BORDA 2019). The percentage of guesthouses and hotels that possess bore wells has increased from 42% in 2009 to 60% in 2010, thereby showing a rise by a factor of 1.5 each year (Gondhalekar et al. 2013). The households, guesthouses, and hotels also extract huge groundwater from their own wells and use flush toilets. Private bore wells pump nearly 0.6 MCM/year of groundwater in the town. A study (Yangchan et al. 2019) indicated that there are about 300 bore wells or hand pumps in the Chemday village of Leh with just 6,000 inhabitants. Lowering of the water table, failure of wells, drying of springs, and low water quality are the signs of the continued abstraction.

Groundwater abstraction and its increasing demand, particularly for irrigation, depleted many aquifers of the world (Konikow & Kendy 2005). The abstraction is highest in Asia at an estimated rate of ∼150 km³/year (Taylor et al. 2013). Withdrawal is a major concern for India, particularly for irrigation, which uses ∼230 km³/year (Rodell et al. 2009; World Bank 2012). Depletion is especially worrisome in the northwest states. The net effect of all the factors on the groundwater is that the storage is lost at a rate of 7–10 mm/year annually (Cao & Roy 2020). While observing the published maps of groundwater withdrawals and storage changes in India (Kerr 2009; Rodell et al. 2009; Tiwari et al. 2009; Cao & Roy 2020), the rate of loss of −5 mm/year in Ladakh is quite worrisome.

Specific yield (Sy) is generally defined as a ratio of change in groundwater mass and water level change (Pool & Eychaner 1995; USGS 2003; Gehman et al. 2009). Assuming a minimum rate of groundwater depletion of ∼− 5 mm/year (Cao & Roy 2020) and a specific yield of 0.3 for granite aquifers (CGWB 2017a, 2017b, 2017c), the average rate of water table decrease would be ∼17 mm/year in the district. The local rates could be highly variable; from negligible decrease in some locations to huge depletion in populous areas. Therefore, estimated annual groundwater storage would decrease by ∼0.7 km³ in the granite aquifer of Leh which has a 39,553 km² area (Table 2). The continued depletion at this rate due to climate change and increasing population will subsequently lead to the withdrawals highly exceeding net recharge.

Groundwater of the Leh district is slightly alkaline (pH 6.9–7.9) and has high turbidity (CGWB 2009; Dolma et al. 2015b) above the desirable limit of 5 Nephelometric Turbidity Unit (NTU). Himalayan Rivers carry huge dissolved matter and suspended sediments (Galy & France-Lanord 2001). The infiltration of the particulate-rich water through the preferential pathways makes the groundwater turbid which is a concern for the aquifers of the region. This process is known to have clogged the pore spaces and reduced the aquifer reserves in many parts of the world (e.g. David et al. 2005). Electrical conductivity (90–480 μS/cm) and chloride (7.1–21 mg/l) are above desirable limits in some aquifers (Dolma et al. 2015b; CGWB 2009, 2020). Hardness varies between 76 to 152 mg/l and the concentration of the inorganic solutes highly varies and generally follows the order; Ca²⁺ > Mg²⁺ > Na²⁺ > HCO₃⁻ > K⁺ > Cl⁻ > SO₄²⁻ (Dolma et al. 2015b; Lone et al. 2020). Groundwater fluoride (0.02 to >1.5 mg/L) and arsenic (1.1 to 86 μg/L) are above the WHO permissible limit of 0.01 and 1 mg/l, respectively (CGWB 2009, 2020). Groundwater iron (0.02–1.96 meq/L) is highest in alluvium and piedmont aquifers and manganese is higher in older alluvium and hard rocks (Lone et al. 2020). Very high trace elements in drinking water have severe consequences and may cause deadly fluorosis and arsenites that kill millions of humans every year all over the world (Jianmin et al. 2015). The inorganic compounds are mainly geogenic and influenced by the water-rock interaction, microbial degradation of organic matter, bacterial diversity, and sedimentation. Deeper groundwater (50–70 m) is generally more mineralized.

The challenges caused by groundwater depletion such as water unavailability, food security, and sustainability in India require effective management policies (Dangar et al. 2021). There are success stories of implementation of several initiatives in different parts of the country (e.g. https://cag.gov.in/uploads/download_audit_report/2021/8%20Chapter-4%20Implementation%20of%20schemes-061c19df3972399.10790639.pdf accessed: 22-11-2023). We stress that researchers, academicians, policymakers, NGOs, and other stakeholders have an important role in prioritizing, adapting, and/or implementing robust and strategic planning for comprehensive management of water resources as per two heads in this region (Figure 8(b)).

• Resource-directed management strategies include governance provisions for socio-economics, sustainable water distribution, and its utilization (Aditi & Shah 2005; Himanshu et al. 2015). The setting of compulsory realistic water-use permits and licensing on well drilling, abstraction, regulation and wise allocation of water, water-saving irrigation, efficient water-use, conservation tools, and engineering solutions have been used in this direction elsewhere (e.g. Livingston & Garrido 2004; Jain et al. 2019). These policies need to be reformed as per existing national strategies (e.g. National Water Policy 2012; Ground Water Management and Regulation 2023) to offer an effective resolution of demand-related problems.

• Similar strategies are needed to reduce the impact of effluent and waste disposal from domestic and industries on water quality (Shankar et al. 2011; Sudarshan et al. 2020; Soumyajit 2022). The Environment (Protection) Act 1986 is a crucial instrument to prevent quality in stressed and vulnerable aquifers through several measures.

• Consortium stakeholder (institutions and users) participation effectively manages resources by inter­intra coordination and community involvement (e.g. Kumar & Saizen 2023a, 2023b). Participatory groundwater management through awareness, workshops, training, guidelines, etc. about the resources makes management successful (Kulkarni et al. 2015).

• Unavailability of data and poorly known systems seriously hinder groundwater management, effective governance, and water planning (Mukherji & Shah 2005). Data analysis makes groundwater visible and estimates the actual reserves. We specifically recommend an emphasis on the collection of quality hydrogeological data in space and time. Prioritized monitoring (well inventory, water level, recharge/discharge, outflow rates, pumping, etc.) and multiple holistic approaches estimate hydrogeological parameters and groundwater reserve with high certainty (Joseph et al. 2018). Registration generates important data about bore wells and improves data quality globally (Molle et al. 2017).

• Long-lasting solutions to these issues require detailed scientific studies involving hydrogeology (Quamar et al. 2020), RS/GIS (Hammouri et al. 2012), geophysics (Wiederhold et al. 2021), chemical/ isotope data (Dar et al. 2021; Modie et al. 2022), and satellite data analyses (Collados-Lara et al. 2021; Martinsen et al. 2022). Evaluation of contaminants and solute transport mechanisms through integrated approaches is needed (e.g. Alam et al. 2012; Kumar et al. 2015; Mogaji 2018; Asmael et al. 2021; Soumyajit 2022).

• Assess the present and future vulnerability of the groundwater to the impacts of climate change and anthropogenic stresses through hydraulic and hydrodynamic models (Toews & Allen 2009), climate models and statistics (Pulido-Velazquez et al. 2021), groundwater models (Llopis-Albert & Pulido-Velazquez 2015), machine learning tools e.g. Soil and Water Assessment Tool and Artificial Neural Network (e.g. Jimeno-Sáez et al. 2018), management models (Gómez et al. 2022), satellite data (Jin & Feng 2013; Long et al. 2016; Collados-Lara et al. 2020), as well as developed methodologies e.g. turn-over time index (Pulido-Velazquez et al. 2020; Baena-Ruiz et al. 2020). Manage groundwater contamination caused by agriculture, industry, and domestic effluents (Kurwadkar et al. 2020).

• Strategic planning in terms of aquifer mapping and assessment at a micro-watershed scale (Jha & Sinha 2009). Planning on groundwater problems and vulnerable aquifers requires practical integrated scientific, engineering, and technical solutions. Interdisciplinary region-specific strategies are required to manage and control the negative impacts on groundwater from land-use change, urbanization, and other human activities simultaneously through integrated water management (Kulkarni et al. 2015; Mitter & Schmid 2021).

• Economic tools of funding, incentives, and R&D projects will promote precipitation harvesting, watershed management, artificial recharge, infrastructure up gradation, and build resilience (Hoogesteger 2022).

• Develop timely infrastructure to mitigate the negative impacts of declined reserves and quality. Tools such as check dams, injection wells, and managed aquifer recharge (MAR) will increase infiltration and groundwater volume (e.g. Paul & Panigrahi 2016; Zhang et al. 2020).

• A regional platform for groundwater data integration is required to provide sufficient measurements and efficient analysis tools for accurate assessment of groundwater resources. It enables the management of groundwater-related information from different sources, facilitates data interoperability between stakeholders, provides access to groundwater data, and enhances decision-making about groundwater management in Ladakh (e.g. El Sawah et al. 2011).

• Integrative groundwater information systems, e.g. INDIA-Groundwater Resource Estimation System (IN-GRES), and the Aquifer Information and Management System (AIMS) need to make the best data available and improve decision-making. The Central Water Commission (CWC), Central Ground Water Board (CGWB), and specialized local regulatory bodies can and shall play an important role in this direction (Jain et al. 2019). However, there are various challenges in implementing such policies in India due to various factors, which need to be minimized at the local level (François & Closas 2020).

Groundwater resources of the Ladakh region have been significantly affected in recent years by the ongoing climate change and anthropogenic processes of population expansion, urbanization, tourist influx, etc. Amplified by the impacts of developmental activities and socio-economic changes, the overall future of water resources is predicted to be declining. Data deficiency and lack of scientific studies on various aspects of the groundwater create major challenges in the assessment of these changes and resources. This study attempts to synthesize the available data to examine the impacts on the storage, quantity, and quality of the resource. Groundwater draft, currently estimated at 172 MCM, has increased rapidly and affected the reserve's quantity and quality. The estimates have some limitations because no spatial and time-series data analysis was provided in the study. It is projected that increasing water demands and low replenishment rates in the region will lead to a faster decline of the groundwater in the future. In Ladakh, warming atmospheric temperature, the erratic behavior of precipitation, loss of winter snowpack, faster glacier/snow melting, and increase in runoff variability are commonly observed impacts of climate change. Significant loss of the cryosphere (ice and glaciers) has reduced the water availability and infiltration processes, thereby posing serious consequences on the health of the aquifers. Population expansion and rapid unplanned development have increased urbanization, and the number of buildings, and caused significant LU-LC changes. As a result, it depleted groundwater resources, increased contamination, and disturbed the natural hydrological processes during the past few decades. In addition, rapid exploitation of the groundwater is another major concern as more wells are drilled through drilling machines.

The unavailability of sufficient quality data and its disparity highlights the need for early measures to be taken up in the region. It will ensure sustainable groundwater management, and utilization, and prevent the emergence of hazardous situations such as shortage of water, reduction of food, and socio-economic discomfort. It is recommended to initiate detailed scientific and R&D programs to characterize the recharge, flow, discharge, and evaluate the groundwater reserves. The integrative modeling of the impacts on water resources will help to achieve the United Nations Sustainable Development Goal (SDG) of climate change adaptation, mitigation, and sustainable development in the region. IPCC WGII Sixth Assessment Report 2021 (IPCC 2021) suggested ‘Confidence is high that strong and rapid mitigation initiatives are needed to avert the manifestation of climate change in all components and features of the global water cycle’.

The first author is thankful to the SCIENCE ACADEMIES' (Indian Academy of Sciences, Indian National Science Academy, and National Academy of Sciences India) for the 2-month summer research fellowships (SRFP – 2021: Registration No. EPST3). The authors acknowledge the availability of groundwater reports of the Central Ground Water Board, Government of India on the website. The Journal Editor and anonymous reviewers are acknowledged for the thorough multiple reviews of the paper. We are pleased that all the reviewers find our research aim interesting and we thank them for a detailed review, valuable suggestions, and improving the quality of the paper. Dr Farooq Ahmad Sheikh, Assistant Professor of English, University of Kashmir proofread the revised manuscript.

Farooq A. Dar and AL Ramanathan designed and developed the manuscript. Riyaz A. Mir helped to prepare the best possible quality figures and write and edit the text. Rayees A. Pir has been instrumental in providing recent data on water levels and groundwater. He also prepared logs, analyzed data, and wrote the interpretations.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.