Monitoring of water resources and vegetation in the Helmand Basin using satellite image time-series and border hydro-political challenges

Since 1987, when the World Meteorological Organization (WMO) stressed the need for research on the impact of climate on water resources, researchers have conducted extensive research on the effects of climate change, specifically in catchments and how it impacts water resources. In South and East Asia, Akhundzadeh et al. (2020) studied the effects of climate change on the Kunduz River Basin in Afghanistan and Luo et al. (2019) studied the effects of climate changes on the Xinjiang River Basin and Xiaowan Liu et al. (2019) on the Yarlung Zangbo River Basin in China. In North America, Kopytkovskiy et al. (2015) studied climate change impacts on the Upper Colorado River Basin, Reed et al. (2020) on the Upper Mississippi River Basin and Shamir et al. (2021) on the Upper Santa Cruz River Basin on the US–Mexico border. Several studies have also been conducted in Europe, such as the studies of Didovets et al. (2020) on impacts of climate change on the Ukraine River Basin, Dorchies et al. (2016) on the Seine River Water Basin and Kay et al. (2019) on the English River Basin. A large proportion of these studies were exercised on finding precise reasons underlying water depletions in river basins with respect to climate change and human interventions as two separate and different agents. That is why some of the more recent literature includes multi-disciplinary approaches required to provide a multi-dimensional analysis of the issues of human (particularly politics) and nature.

More recent researches are directed at the study of climate change along with other more human and social implications at river basins. This multi-dimensional or say complementary regulation to account for different factors has oriented researchers to pursue more accurate methods for assessing climate change effects. The complexity of the impacts brought on by these factors is so great that some researchers have used conceptual-socio-hydrological models, in which a combination of human and climatic factors affecting water resources are evaluated. The impact of various human and natural factors on water resources has formed an interdisciplinary field of study demanding the use of more accurate methods of evaluation (Yang Liu et al., 2019; Bertassello et al., 2020; Viola et al., 2020).

In Asia, a large portion of which lies on the global dry belt, the impact of climate change on watersheds and water resources has been greater and closely linked to more complex social and political issues. Climate change in these areas is mainly concerned with the process of economic and social modernization and growth of modernism and industrialization, leading to burgeoning populations and the immethodical expansion of cities. Climate change in border regions has also challenged the frame on territorial borders, which as opposed to the flow of goods and capital, climate change is considered an extraterritorial issue and cannot be managed by border laws and regulations. Therefore, the formation of a deep stream of knowledge in theories of international relations is necessary to solve the challenges of climate change (Benzi & Persoon, 2019) which in other words is addressed as one of the main issues of modern climate policy (Peterson, 2021). The core issue leading to border disputes between the neighboring countries is a lack of consensus on the prime cause (climate change or human intervention) of water depletion in border rivers, which is a main objective of this study.

The recognition of legal frameworks for resolving border disputes between India and Pakistan in the Indus River Basin (Qureshi, 2018), conflicts between Laos, Vietnam, Cambodia, and Thailand over Mekong River in South Asia (Kittikhoun & Staubli, 2018), environmental changes in the upstream area of the river Gong and the debates between India and Bangladesh (Rahman et al., 2019), and the Aral Sea Crisis are examples of environmental tragedies in the 1960s which have lingered into the 21st century (Li et al., 2021). The central issue of conflict between the countries in all the mentioned studies, as in the case of the present study, are directed at the prime cause of water depletions in the river downstream. The stretch between whether the shortages were due to climate change or upstream developments by neighboring countries has led to new multi-disciplinary researches, primarily hydro-political in topic.

In the Middle East and North Africa (MENA), the impacts of climate change on water resources have been more complex due to its relationship with political issues. As Gray & Dolatyar (2000) have argued, water environmental issues in the region have been overshadowed by other political, military, and economic approaches, the issue of which has made it difficult to overcome crises in the area. Other researches on environmental changes (natural and anthropological) include studies on Nile River and conflicts between Ethiopia, Egypt, and Sudan (Swain, 1997; Ramadan et al., 2021) and Tigris and Euphrates river basins (Dohrmann & Hatem, 2014; Kibaroglu & Sayan, 2021) and the conflicts therein between Turkey, Syria, and Iraq, which still remain a main border issue between the countries.

The ‘Helmand’ River in the Hamun region, situated in the borders between the two countries of Iran and Afghanistan and separating the two regions of South and Southwest Asia, requires a thorough investigation as it is simultaneously exposed to environmental issues, environmental change, and political issues between the governments of Iran and Afghanistan. The hydro-political disputes between the two countries around the Helmand River have a 100-year history and the cause of low water levels in the downstream basin has long been disputed in all periods. From the very first treaty concluded between the two countries of Iran and Afghanistan by the arbitration of the British government in 1872, the two countries were required to refrain from conducting any operation on the river that would reduce water levels according to the provisions of the treaty (Mojtehedzadeh, 1995). But in the following years, changes in water levels, affected by various factors such as drought, flooding of river, and/or manipulations in the upstream basin have extended disputes between the two countries, concluding on several legal agreements between the two countries (Hafeznia et al., 2006). Since the signing of the most important water agreement between the two countries in 1972, wherein the amount of Iran's water right was set at 26 m³/s (Documents of the ministry of foreign affairs of Iran, 1977–1979) until now, the volume of water has continuously reduced, to the point of reaching complete depletion in certain years. The Afghan government has blamed severe droughts in recent years for the shortage of Helmand water, whereas the Islamic Republic of Iran believes that the reason for the sharp decline in Helmand water is not the drought at the river downstream, but rather measures taken by the Afghan government to construct facilities on the Helmand River, thereby changing the water direction in contradiction to the 1972 agreement. Although serious depletion of the Helmand River water in Iran has not yet become a matter of tension between the governments of Iran and Afghanistan, and their differing views on the issue requires that the actual causes be scientifically assessed.

The main purpose of this study is to investigate the prime cause of reductions in water levels to the Helmand River through monitoring changes in vegetation and water levels and its effects on downstream basins using Landsat images’ time-series. Monitoring vegetation, as one of the important variables of land use change, is a suitable way to analyze the issue at hand and verify the hydro-political claims of the two governments of Iran and Afghanistan and clarify the impact of measures taken at the river upstream in terms of agriculture and residential use. One of the main measures adopted in the compilation of development plans is the preparation of land cover maps used in the management of natural resources and environment (Shetaii & Abdi, 2008). Landsat images, in particular, are a conventional source of reference in the literature given their long statistical period (since 1973 up to the present time) and having appropriate spatial, spectral and radiometric resolution. Various algorithms have been proposed in order to classify these images and prepare user maps that can be generally categorized into two groups of common and advanced methods (Fatemi & Rezaei, 2006). Among those of the first category (common) include: K-Means and ISODATA methods or variable averages, Maximum Likelihood Classification (MLC), and Minimum distance methods (Mahesh & Mather, 2003). None of the methods can comparatively outperform the other (Jensen, 2005), albeit, the MLC method has been named one of the most accurate and common classification algorithms of the first category. Another accurate model for generating land cover maps, as suggested by Rudke et al., (2021), Gharaibeh et al., (2020), Rana & Venkata Suryanarayana, (2020) is the Support Vector Machine (SVM). Among other contending methods include CA and ANN models alongside TM and ETM+ sensor images (Otukei & Blaschke, 2010; Al Kafy et al., 2021). Landsat images are a suitable source of reference in this case due to their high temporal resolution and data availability and can be incorporated to generate land use maps in the Helmand Plain as a relatively suitable option for studying vegetation changes in recent decades.

Landsat 5 and 8 images were used to monitor vegetation and water. The monitoring time-series was procured from 1991 to 2020, among which images from August were solely used to monitor vegetation. Specifications of the satellites and images are given in Table 1.

The Google Earth Engine (GEE) is a web-based system that provides a variety of remote sensing procedures by incorporating powerful satellite imagery database with simple commands. Conventional methods in remote sensing projects include the preparation of images based on the purpose of the project, followed by preliminary processing (geometric and radiometric corrections), secondary processing and accuracy assessment. Each step includes its own complications such as lengthy preparation time for images, large volumes data to be downloaded, special software and hardware requirements for image processing. The GEE¹ is the best alternative to carry out remote sensing projects which authorizes web applications to run on Google servers. Therefore, creating, maintaining and managing traffic and data can easily be enforced in the system.

Global precipitation measurement (GPM) is a more accurate alternative to Tropical Rainfall Measuring Mission (TRMM) data – often considered the next generation of TRMM – launched in February 2014 by the National Aeronautics and Space Administration (NASA) and the Japan Aerospace Exploration Agency. The Ku/Ka band Dual Frequency Precipitation Radar (DPR) and the GPM Monitoring Imagery (GMI) incorporated into the GPM system can detect both solid and small precipitation (0–1 mm/day). Like the TRMM, GPM can detect rainfall even in tropical regions (Zhou et al., 2020 quoted from Draper et al., 2015).

The Gravity Recovery and Climate Experiment (GRACE) satellite estimates Terrestrial Water Storage (TWS) data such as soil moisture, groundwater levels, water from ice and snow on a monthly basis and can measure ground water storage change caused by both natural and human factors. GRACE data have mainly been used to this day for measuring groundwater changes around the globe. GRACE satellite and Global Land Data Assimilation System (GLDAS) data are considered different hydrological parameters that can be obtained by combining data from Land Surface Models with observation data followed by statistical assimilation (Moiwo et al., 2009). GRACE and GLDAS hydrology products help increase human understanding in relative issues (Rodell et al., 2004).

Both of the satellites used in the GRACE mission are products of NASA and the German Aerospace Center (DLR) that can detect groundwater storage changes (Chen et al., 2009) by means of measuring changes in the earth's gravitational field based on a latitude reference.

One of the main complexities of the SVM model is its restrictions on linear classification of data when using a linear kernel. In the case of remote sensing data, an RBF kernel produces better results (Van der Linden, et al., 2009). When using an RBF kernel, the accuracy of the SVM algorithm can be adjusted in terms of parameters C and g, where C (penalty parameter) is a constant that establishes balance between the decision-making margin and the number of training samples placed on the wrong side of the margin, and g is the kernel width. There is no general rule known in advance for selecting the values of these parameters. Both parameters depend on the scope of data and the data distribution and can vary from one classification to another (Foody, et al., 2006). The SVM is able to overcome problems such as low number of training data, nonlinear distribution of classes, and high number of layers used in classification (Burges, 1998). These capabilities have made ‘SVM’ a suitable option for this research.

Following is a flowchart of how the SVM algorithm works:

One of the main objectives of this study was to investigate the status of drought in the Helmand Basin which can be fully realized by monitoring patterns of precipitation. Based on the precipitation graph obtained from the GPM data, it is evident that the area witnessed a relative increase in precipitation from 2000 to 2021, i.e. total rainfall was increasing throughout 2000–2021 with no reductions therein.

Figure 5 illustrates GRAC data on groundwater status in the basin, which as evident, has decreased significantly throughout the period from 2.1 cm thickness in March 2003 to −5.8 cm thickness in March 2015. This is equivalent to 176% decrease in groundwater in only 12 years. As the values in Figure 5 show, the decreasing trend in groundwater levels in the Helmand Basin are such that no positive values can be observed from March 2011 onwards. Given the relative increase in precipitation during this period (Figure 4), the significant decrease in the Helmand Basin groundwater levels is most likely an indication of high magnitudes of groundwater exploitation during a short-term period of a few years.

As can be observed in Figure 6, waterbodies in the downstream sections of the basin have significantly depleted throughout the interval from 1991 to 2020. An instance of this can be seen in the total depletion of Godzareh drainage (a large wetland located at the lowest parts of a drainage south of Afghanistan) from 1991 to 2020 located downstream Helmand River.

The area percentage graph for the SVM model, as shown in Figure 7, indicates a 566% decrease in waterbodies of the area from 1991 to 2020 (30 years), i.e. waterbodies comprised 2% of the total basin area from 1991 to 1995, later decreasing to 0.3% in the interval from 2016 to 2020. This significant decrease (to the point of near-complete depletion of water bodies) during the 30-year period is also evidenced in Figure 6 for the lowest parts of the basin – regions entering Iran territory.

From Figure 8, Godzareh drainage, located at the lowest part of the Helmand River before entering southwest Afghanistan, has significantly lost any permanent water inlets, such that from 2016 to 2020, no significant signs of water can be seen in the area apart from a few seasonal craters as shown in the figure.

According to data, the maximum number of permanent (or recently turned permanent) and seasonal waterbodies throughout 1984–2019, have been observed in the Upper Helmand catchment. Accordingly, the maximum number of newly permanent and seasonal waters have also been observed in the Lower Helmand Basin in the given time period. Maximum losses of permanent and seasonal waterbodies or permanent waterbodies turned into seasonal and waters in permanent or seasonal holes throughout the time period was seen in the Sistan catchment area of Helmand. The conclusion that can be obtained from this table in line with the research problem is that the maximum amount of newly created permanent waters has occurred in the Upper Helmand River Basin, i.e. Upper Helmand.

Hence, despite findings from GPM precipitation data indicating stable precipitation throughout the time period, the decreasing trends in groundwater levels alongside increased vegetation in Upper Helmand and the loss of permanent waterbodies at the basin downstream, are an indication that the groundwater usage is being led at the basin upstream under the auspices of Afghanistan. Alternatively stated, the usage of both surface and ground water sources by Afghanistan is quite evident.

The study of the effects of environmental changes in basins and water resources has been a chief topic for in recent years. In areas where environmental changes are caused by both natural and human factors, in addition to environmental effects and consequences, legal and political issues created in the relations to involved countries are grounds for thorough investigations in the issues thereof.

Such issues are particularly important in South and Southwest Asia, where the environment has been constantly plagued by domestic and foreign political interference since the beginning of modernization. Imposed borders, which are the legacy of the colonial era in this region, are now imposing their negative consequences mostly in small river basins. The environmental crisis of transboundary Tigris and Euphrates basins (including Turkey, Syria, and Iraq) is due to both natural factors, i.e. drought and widespread human factors which has been created as a result of burgeoning population growth, war, underdeveloped agricultural activities, creation of lakes, deliberate drying of swampy lands and generally inefficient management of water resources (Darvishi Boloorani et al., 2021). The magnitude of the environmental crisis resulting from environmental changes at the Tigris Euphrates river basin is particularly more descendent upon Iraq, which is located further from the river upstream. Dam constructions at the river upstream by Turkey have tapered water flows into the downstream sections of the basin leading to the drying out of groundwater resources and the loss of vegetation, particularly in the eastern plains and deserts of Iraq. The most notable environmental repercussion from this course of action is the phenomenon of haze and dust which is strongly felt by both Iran and Iraq – specifically in metropolitans. Turkey has repeatedly claimed environmental change as the prime cause of reduced river flows, albeit the reasons are more apparent than claimed. The same could also be stated in regards to conditions at the Helmand River in Iran, with the slight difference that the prime cause of reduced water flows at the Helmand River downstream have remained in a cloud of ambiguity and require a meticulous investigation. The water conflicts of the Nile transboundary basin, which are related to human factors especially population growth and various development projects, can also be studied within the framework of this approach (Ramadan et al., 2021).

The Helmand River, as part of Iran–Afghanistan water border, has sparked a widespread controversy in a 100-year period, i.e. since the first agreement inked between these two countries. Helmand is the longest river in Afghanistan which accounts for more than 40% of its surface water. Therefore, the Helmand River is considered a vital resource for the country's southern and southwestern provinces. On the other hand, this river is the main water source in eastern Iran which has a very significant impact on its security, agriculture, economy, and environment, and any changes in the flow of the river can have a significant impact on Iran's interests from the river. Reduction of river water in the downstream basin, as the most important disputed issue between the two countries, has been turned into a complicated issue due to the impact of both climatic factors (drought) and human interventions in at the river upstream. The findings obtained from monitoring precipitation, waterbodies, and vegetation in the river basin, showed that human interventions at the upstream basin have caused a decrease in river water flows, causing widespread environmental disasters at the downstream basin and exposing large human populations, especially in Iran, to a water crisis.

In line with the main objective of finding the prime cause of reductions in water levels at the downstream section of the Helmand River, the present study attempted to classify different waterbodies throughout a 30-year period. As the findings suggest, the highest loss of waterbodies in the region throughout the 30-year period has occurred at the downstream section of Sistan/Helmand and the Lower Helmand Basins. Monitoring results on waterbodies for the 30-year period were obtained using Landsat time-series images which showed comparable results with those of Section 3 (GSW) indicating significant reductions in water levels at the inlet into Iran.

The findings of the research show that during the years 2016–2020, water storage procedures (both natural and artificial reserves) have occurred in two upstream basins of the Helmand River, namely Upper Helmand and Upper Arghandab. The 226% increase in water levels in this period is unprecedented as compared to the previous periods. Another issue, according to Figure 10, is the near-complete depletion of Godzereh during 2016–2020, which is an environmental disaster of its kind. The 74% reduction in water level in the Sistan–Helmand catchment area, which also encompasses Godzereh, is clearly confirmed in Figure 10 over a 30-year period. Furthermore, according to Figure 8, declining water levels in other downstream catchment areas can be detected over the 30-year period (from 1991 to 2020). It is therefore highly likely that water storage measures are taking place in very large beds by humans in the Upper Helmand catchment area in Afghanistan and more research should be done in this regard. Also, increases in water levels at the upstream sections of the basin are quite evident in the depths of Afghanistan, with decreases towards the downstream of the catchment area as well as the inlet into Iran during the 30 years (its peak in 2016–2020).

Figure 11 shows vegetation covers monitored in the region, indicative of 19% increase in vegetation in the Upper Helmand Basin between 2016 and 2020. The 19% increase for an area of about 48,000 km² is a significant value, and it is thought that Afghanistan, be it controlled or uncontrolled, has embarked on increasing cultivation in the area. On the other hand, precipitation measurements demonstrate stable rainfall throughout a 21-year period (Figure 4), rainfall being the primary supply of water. This in conjunction with the decreasing trend in groundwater levels (based on GRACE data Figure 5) and coinciding increases in poppy field cultivation in Helmand Province (Figure 12) clearly points to the usage of surface and groundwater resources for human interventions in Afghanistan. Therefore, it can be concluded that Afghanistan has used surface and groundwater sources from the Helmand Basin for various purposes including agriculture, etc. The aftermath of this is a significant decrease in water levels at the river downstream. Other notable facts regarding this area as obtained by the findings are:

• Stable precipitation and rainfall conditions as shown in Figure 4.

• Reduced groundwater levels in the basin (Figure 4) despite stable rainfall.

• Increased poppy cultivation concurrent with decreased groundwater levels in the basin (Figure 12).

• Loss of more than 507 km² of permanent waterbodies in the Sistan/Helmand Basin at the lowest parts of the catchment and the border into Iran (Table 5).

• A significant decrease of 1,057% in waterbodies as per classification results shown in Figure 10.

Another important issue is the decrease in the water flow of the Helmand River in recent years. A report entitled ‘Sistan Plain Water Resources’ (2004) prepared by the Office of Infrastructural Studies of the Ministry of Energy shows that the water flow (debi) of the Helmand River has sharply decreased during the years from 1999 to 2003. Another study by Khosravi (2010) in this field has shown that the water levels of Hāmūn-e Puzak, Hāmūn-e Sabari, Hāmūn-e Helmand lakes have decreased significantly between 1992 and 2004, whereas the water level of Hamun Helmand has been much higher during these years. In general, the decrease in water flow of the Helmand River from 1996 to 2016 has left a great impact on soil degradation in the southeastern region of Iran (Rahimi et al., 2020).

The study of historical trends in legal treaties between the two countries of Iran and Afghanistan over the past 100 years also shows the changes taken place along the river in the upstream basin and the Iranian government's protests against it. Although all legal treaties between the two countries have explicitly prohibited the two countries from any action that would reduce river flow, complexities related to reducing water levels as well as historical involvement of major powers in drawing up treaties have led to different interpretations and the eventual continuation of conflicts between the two countries. In the ruling issued by Goldsmid, representative of the British government in demarcating borders of Iran and Afghanistan in 1872 (Latter dated 16, May, 1871 from Indian government to Goldsmid) followed by the McMahon Treaty in 1905 (Documents of the ministry of foreign affairs of Iran, 1905), which was concluded with the intervention of Britain to resolve the Helmand River problem, political interpretations were left out of the terms and conditions of the agreement and this issue paved the way for further disputes between the two countries. In all the following years, the government of Afghanistan, using its upstream position and with the pressure exerted on Iran by the great powers (Britain and the United States), carried out operations along the river, with no cessation of actions even with the conclusion of numerous treaties. After the failure of negotiations on the Treaty of Vadadiyeh and Taminiyeh, which set up a joint commission to investigate the water issue in 1927 (Documents of the ministry of foreign affairs of Iran, 1931), uncontrolled and immethodical extraction of water and diversion of rivers through canals by Afghanistan at the upstream section of the basin caused a severe decrease in volume of water in the Sistan region of Iran and this issue led to the conclusion of temporary contracts in 1936, 1937, and 1938 between the parties. In these agreements, the parties were committed not to reduce the share of the other party by any actions of their own (Documents of the ministry of foreign affairs of Iran, 1936, 1937, 1938). In 1951, Afghanistan's efforts to build dams and divert water from the Helmand River increased and this issue drastically reduced Iran's share of Helmand waters in such a way that reductions in the volume of water in the Helmand River caused losses to farmers in the Sistan region (Description of the delegation to Washington on the Helmand river, 1956). In the same decade, the dipolar conditions of the Cold War and the US–Soviet effort to infiltrate into Afghanistan led to large loans that were granted to Afghanistan for the purpose of constructing a dam on the Helmand River and this issue exacerbated the continuation of conflicts between the two countries of Iran and Afghanistan. Afghans continued to reduce Iran's share of water from the Helmand River. In the meantime, the United States could not give a negative response to Afghanistan's demand. Under US pressure, Iran was forced to become less involved in Helmand issue which opened the stage for Afghanistan to intensify its efforts to reduce Iran's share of water from the Helmand River (Documents of the Iranian ministry of foreign affairs, 1962). In late 1960s, with the drastic reduction in the volume of water inlets into Iran, an unprecedented water shortage occurred in Iran's Sistan region, inducing the migration of villagers to cities and severe losses to farmers. Although the dipolar atmosphere and specifically US pressure prevented Iran from complying with its demands, with repeated appeals by Iran in 1972, the treaty of division of Helmand water, which is the last and most important treaty over the division of water from this river, was signed between the parties. In this treaty, the amount of Iran's water rights was set at 26 m³/s which did not meet the needs of the Sistan region. According to the treaty, Iran could not request for more than this amount and Afghanistan could excessively exploit the water in anyway it needed (Documents of ministry of foreign affairs of Iran, 1977–1979). In those years, Iran, under the pressure of United States, renounced its demands, so that Afghanistan would not turn to the Eastern Camp. It seems that this agreement has not been able to end the disputes between the two countries. Since then, Iran's share of water has steadily decreased due to the 1972 Treaty and uncontrolled and immethodical abstraction of water for agricultural irrigation of poppy fields in the upstream section of the basin, as highlighted in UNODC reports (2012, 2018) which has had destructive environmental and human effects in the downstream sections of the basin, especially in Iran (UNEP, 2006).

Given the legal background and findings from evaluations on water flows in the river, the prime cause of decreases in water flow at the river downstream, particularly in Iran, is not due to climate change, but rather human interventions and exploitations at the upstream sections in Afghanistan. Despite the prohibition of any excessive exploitation of waters from the river in numerous conventions between the two governments of Iran and Afghanistan, operations continue to exploit waters from the upstream section. The resulting decreases of water flow to the downstream sections has left a huge impact on the eastern regions of Iran. Some of the more notable repercussions of these actions that can be mentioned are the drying out of numerous lakes and wetlands, loss of vegetation and increased dust and haze, collapses agricultural economy and migration of populations due to water shortages.

Despite numerous legal treaties which were concluded between Iran and Afghanistan over the past 100 years regarding the status of the Helmand River, reduction of water of river in downstream basin and its causes have remained a bone of contention between the two countries. Study of historical trend of conclusion of these treaties shows the repeated protests of Iranian government in all periods against the moves taken by Afghan government in the upstream basin which often led to the conclusion of a new treaty with intervention of a third country including Britain and the United States. The results of this article showed that sharp decline in water of the Helmand River in recent years in continuation of the same historical trend of the past is related to human interventions led by Afghanistan at the upstream basin.

The findings of this study can be summarized as follows:

• As shown by GPM data on precipitation (Figure 4), rainfall in the Helmand River has been stable throughout the years, and being a main supply of water in the basin it can be said that no impactful dry periods have occurred in the study time period.

• GRACE data on groundwater levels of the Helmand Basin (Figure 5) show significant decreases in groundwater levels, especially at the downstream basin, indicative of groundwater exploitations by Afghanistan at the upstream basin.

• Correlations and overlaps between GRACE data on groundwater levels and statistics and graphs of poppy cultivation in Afghanistan (Figure 12) proposed by the UNODC are indicative of the type of water exploitations in the Helmand Basin. The concurrency between decreased groundwater levels and increased poppy cultivation in Afghanistan from 2011 onwards (peaking in the years 2016 and 2017 as shown in the proposed documents) is evidently a sign of groundwater exploitation occurring at the upstream section for the irrigation of poppy fields.

• Results from an SVM classification of vegetation and waterbodies throughout the study area showed reasonable results with high accuracy and kappa value. The results showed clear indications of the loss of waterbodies. According to Figure 10, waterbodies were significantly depleted in the downstream basin, with the majority of waterbodies dried out. At the same time, as shown in Figure 11, vegetation has increased in the Upper Helmand Basin.

• GSW data on the Helmand Basin also indicated the loss of permanent waterbodies in some regions in the downstream basin and at the border with Iran. The results obtained from GSW data, as given in Table 5 and Figure 8 also allude to water exploitations at the Upper Helmand Basin as the prime cause of decreased water flow to the downstream section.

• It can be concluded that the prime cause of decreased water levels in the downstream sections of the Helmand Basin is due to human interventions led by Afghanistan at the upstream basin, contrary to what was claimed as climate change. This has led to reductions in water flow and both environmental and human-led degradation at the lower sections of the basin, particularly at the border with Iran. A resolution to this conflict requires the commitment and cooperation of both involved countries in executing the terms of the 1971 treaty, without any third-party interventions.

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

The authors declare there is no conflict.