Flood‐oriented watershed health and ecological security conceptual modeling using pressure, state, and response (PSR) approach for the Sharghonj Watershed, South Khorasan Province, Iran

Today, watersheds have changed under the influence of various environmental and human factors, and their expected performance has decreased in terms of meeting human needs, providing natural responses, and reducing environmental risks. However, evaluating health status and its impact on various factors has not been given enough attention. To this end, an attempt has been made to evaluate the health and ecological security of the subwatersheds of the Sharghonj Watershed using the pressure‐state‐response approach emphasizing flood‐related issues in the region. Toward that, 21 preliminary hydrological, anthropogenic, natural, and climatic criteria were selected. The preliminary variables were then finalized based on the results of the collinearity test and the data availability. The final variables were appropriately allocated to pressure, state, and response (PSR) indices, and associated health and ecological security indices were determined at the subwatershed scale. The results showed that the PSR ranged from 0.56 to 0.86, 0.46 to 0.84, and 0.35 to 0.96, respectively. Health and ecological security also varied from 0.53 to 0.83 and 0.27 to 1.01 in different subwatersheds. Eventually, the weighted mean PSR indices for the Sharghonj Watershed were 0.72, 0.67, and 0.73, respectively. The weighted mean health and ecological security indices were 0.70 and 0.68, respectively. The research results indicated that the dynamic of various variables related to floods considerably affects the health of the Sharghonj Watershed. It could be concluded from the results that the Sharghonj Watershed is highly flood‐susceptible, whose health and ecological security status was mainly controlled by the damages due to the destruction of residences and orchards by floods in the past few years. The results of the current study provide an appropriate roadmap to the decision makers and planners for the better management of the watershed resources in the region through allocating adequate financial support and implementation measures to priority subwatersheds.


| INTRODUCTION
The development of industry, increase in polluting resources, and human intervention in natural ecosystems to provide welfare and food resources for the ever-increase population of the world caused land degradation (Farzi et al., 2022;Hashem & Marrouch, 2023;Nasiri Khiavi et al., 2023;Sadoddin et al., 2016), changes in vegetation and soil (Hazbavi, Baartman, et al., 2018;Hazbavi, Keesstra, et al., 2018;Toma et al., 2023), deforestation (Gompil et al., 2022;Mehdi et al., 2015), climate change (Chamani, Moradi Rekabdar Kolaei et al., 2022;Mohammadlou et al., 2022).The results of such degradations have mirrored in widespread and extensive flood occurrence, land subsidence, and accelerated soil erosion leading to unexpected and sometime uncontrollable natural and socioeconomic disasters (Eslamian & Sabzevari, 2022;Tanoue et al., 2020).Also, the performance of the watersheds in providing different services is dynamic over time under the influence of changes in watershed characteristics attributed to land-use, water quality and quantity, climate, population, and socioeconomic conditions.Accordingly, regular health assessment of the watersheds provides a proper baseline showing how far the system is from the climax status, based on which appropriate remedial decisions can be efficiently made.The unhealthy and disorderly situation of the watershed results in many unwanted outcomes, viz., floods, droughts, severe soil erosion, dust storms, biodiversity loss, and socioeconomic tyrannies.In the meantime, floods have intensified in recent years following climate change and human interference, causing financial losses and loss of life in many parts of the world, which has attracted great concern for laypeople and governments (Aksoy et al., 2016;Arantes et al., 2023;Chamani et al., 2023;Nikouei et al., 2023).Considering the nature of flood and its many direct and indirect effects on human life and other beneficiaries, it is necessary to use appropriate indicators to know the health status and performance of watersheds (Arantes et al., 2023).However, a systematic best management practices-based procedure for zoning watershed health from the viewpoint of flood and assessing determinant factors leading to cost-effective and efficient flood mitigation plans is scant.Floods are significant as a type of non-permanent surface flow, both from management, hydraulic and structural viewpoints (Meresa et al., 2022).This has affected the health of watersheds more than in the past and has caused significant disruptions in the provision of watershed services (Mosaffaie & Salehpour Jam, 2018;Mosaffaie & Salehpour Jam, 2020;Sadeghi et al., 2005;Sadoddin et al., 2010).On the other hand, evaluating the capability of a system to provide the expected functions depends on the system's health (Jahandari et al., 2022).Nonetheless, flood management is still challenging due to its complexity, scale, and multidisciplinary nature.Flood control and mitigation are, therefore, multisector treatments whose integrated management needs identify the entire watershed's health status from the flood occurrence viewpoint to balance human needs and natural capacities.Such an approach improves the social and economic status of the people and ultimately leads to sustainability (Ali et al., 2019;Mirchooli & Sadeghi, 2018).
The health status of the watershed can be determined by the ability of ecosystems to maintain, self-regulate and restore their capability to provide different services after subjecting to various levels of tension (Li et al., 2014;Suo et al., 2008).Therefore, a watershed health assessment is the best framework for identifying problems and influential variables in sustainable watershed management.Watershed health assessment is valuable for evaluating and identifying effective human, ecological, and environmental resource management strategies (Ebrahimi Gatkash & Sadeghi, 2022).Therefore, it is necessary to maintain the watershed's health to maximize its services and, as a result, improve human welfare.Evaluating the watershed ecosystem health is one of the basic principles for decision-makers and managers to prioritize managerial activities for achieving efficient adaptive management (Sadeghi et al., 2023).Considering the nature of flood and its direct and indirect effects on human life and other beneficiaries, it is necessary to use appropriate indicators to know the health status and performance of watersheds.Different approaches are used to assess watershed health (Chamani, Vafakhah, et al., 2022); among them, the conceptual framework of pressure, state, and response (PSR) was proposed by the Organization for Development and Economic Cooperation in the late 1990s.In this framework, human factors are also considered in addition to the natural health characteristics of ecosystems.Different approaches are used to assess watershed health (Chamani, Vafakhah, et al., 2022), among which the conceptual framework of PSR was proposed by the Organization for Development and Economic Cooperation in the late 1990s.In this framework, human factors are also considered in addition to the natural health characteristics of ecosystems (Hazbavi, Baartman, et al., 2018;Hazbavi, Keesstra, et al., 2018;Liu & Hao, 2016;Sahana et al., 2022).The PSR framework is often combined with remote sensing data to assess watersheds' health (Sahana et al., 2022).In the same context, Ding et al. (2008) assessed the health of the region of Inner Mongolia in China.The results obtained from applying the PSR framework have shown that only 18% of the entire area in the northeastern parts is healthy.Yang et al. (2015) investigated the health of wetland ecosystems in China.They accordingly assessed the effect of remedial and revitalization operations, viz., construction of embankments and tidal ports, land reclamation, road construction, and dam construction in the upstream areas on wetland ecosystem health with the help of the PSR framework.The results showed that from 1950 to 2010, the ecosystem health index declined due to increased pressure on wetlands.Sun et al. (2019) used the PSR conceptual approach based on 27 ecological, social, and economic criteria for assessing the watershed health in the Gulf Wetlands Jiaozhou in China for the node year 2015.Based on the results, the bay's condition was assessed as unhealthy.Das et al. (2020) effectively documented the application of the PSR model to the ecosystem health condition of wetlands in West Bengal, India, from 2013 to 2020.According to the findings of this study, this area has been impacted by human pressures such as population density, urbanization growth rate, and road density, which has resulted in the degradation of the environment and decreased health.Hazbavi, Parchami, et al. (2020) studied the status and spatial changes in the health of the Kozeh Toparaghi Watershed located in Iran using 27 different hydrological, human, and climatic criteria at 36 subwatersheds using the PSR framework.Hazbavi, Sadeghi, et al. (2020) used the PSR conceptual framework based on 17 climatic, human, and hydrological criteria to assess the health status of the Shazand Watershed in Iran in 4 years 1986, 1998, 2008, and 2014.The results assigned about 53%, 77%, 78%, and 60% of the Shazand Watershed as relatively unhealthy conditions in 1986, 1998, 2008, and 2014, respectively. Li et al. (2021) ) extended the PSR framework to assess the health of a Chinese rangeland ecosystem.They also confirmed the geographical distribution of ecosystem health across the study watershed.As a result, between 2000 and 2015, the watershed health worsened from southwest to northeast.Furthermore, Su et al. (2021) effectively assessed river health in wet and dry seasons using PSR and M-HSC models.In the wet season, the PSR and M-HSC techniques demonstrated the same level of health.In contrast, during the dry season, PSR better represents the real condition than M-HSC.They also confirmed that PSR is more beneficial for measuring the effects of human disturbances on river health in urban rivers.Sadeghi et al. (2022) evaluated the effectiveness of existing check dam structures in the Darwazeh Qur'an Watershed of Shiraz City, Iran, on the watershed's health using the PSR conceptual approach focusing on floods.The results showed that the health index of the study watershed without considering the watershed structures and the stone-cement check dams were 0.55 and 0.53, respectively, confirming the lack of significant impact of the structures on the watershed's health.Ebrahimi Gatkash and Sadeghi (2022) prioritized the Mikhsaz Watershed subwatersheds in Western Mazandaran, Iran, based on health conditions and with the help of different effective and problem-oriented criteria using the PSR conceptual framework and SWOT.The results showed that the main problems of the watershed are limited soil depth, changes in the land-uses, and high specific soil erosion.Health and ecological security atlases for the Pishkoh Watershed in Yazd using the PSR conceptual model framework were developed by Sadeghi et al. (2022).The study revealed that around 91% and 9% of the watershed are relatively healthy and relatively unhealthy, respectively.In contrast, the ecological security index revealed that approximately 41% of the region is classified as relatively unhealthy.Ghabelnezam et al. (2023) also zoned the health status of the Kuzeh Taparaghi Watershed in Ardabil Province, Iran, by combining fuzzy logic operators and the PSR conceptual framework.Sadeghi et al. (2023) used the conceptual PSR method in conjunction with 26 criteria related to various hydrologic, anthropogenic, and climatic aspects to assess the health and ecological security of the Galazchai Watershed in Oshnavieh Township, West Azerbaijan Province, Iran.The watershed's health index varied from 0.388 to 0.688.Over 64% and 58% of the watershed's area was in relatively healthy conditions and moderate ecological security, accordingly.Recently, Zhang et al. (2023) used the PSR model to assess China's ecological security condition thoroughly.The results revealed that the pressure index was the greatest and the state index was the lowest of the assessment indices.They also stated that the ecological security index more properly detects the ecological challenges of each region.
Scrutinizing the literature review results verified the spatial changes in the health status in the entire studied watershed.It further proved the necessity of problem-oriented studies in the context of the watershed health assessment leading to meaningful solutions.Floods occur in the Sharghonj Watershed due to its steep slope and intensive spring rainfall, notably in the eastern and southeastern regions.Furthermore, placing residential areas and barberry orchards in river floodplains has exacerbated the region's sensitivity to floods.Figure 1 depicts some perspectives on floods and regulating circumstances.However, the need for flood-based health assessment and related ecological security is apparent.The present endeavor was planned to assess the health status and ecological security of the Sharghonj Watershed in South Khorasan, focusing on regional flood issues.
F I G U R E 1 Geographic location, land-use/cover map, and flood effects and occurrence of the Sharghonj Watershed in South Khorasan Province, Iran.

| Case study
The Sharghonj Watershed, with an area of 9487.7 ha, is located in the northern part of Birjand City in South Khorasan Province, North Eastern Iran.The mean slope of the area is 23.85%, with maximum and minimum elevations of 2335 and 1568 m.The mean annual precipitation of the watershed is 210.2 mm.Regarding land use, rangeland, outcrop-dominant areas, rainfed land, irrigated agriculture, barberry orchards, and residential areas can be seen in the watershed (Chamani, Moradi Rekabdar Kolaei, et al., 2022).Precipitation in the spring in the Sharghonj Watershed is often torrential rains and sometimes hail, which mainly causes flooding and damage in the eastern and southeastern regions.The flood magnitude has not been recorded in the region due to the lack of a hydrometric station.However, it was found during the field surveys that spring floods with discharge beyond 135 m 3 s −1 seriously damage the barberry orchards in the floodplains.Figure 1 shows a general view of the study watershed, flood occurrence, and damages to barberry orchards.

| Conceptualization of the PSR framework
The PSR framework is a conceptual model that employs the causal connections between environmental, economic, and social elements to build a link between three indicators of PSR (Hazbavi, Parchami, et al., 2020;Hazbavi, Sadeghi, et al., 2020).The Organization for Economic Co-operation and Development (OECD) first introduced the PSR framework to support environmental policy, but it is now used globally to analyze ecosystem ailments (Chamani et al., 2023;Hazbavi, Parchami, et al., 2020;Hazbavi, Sadeghi, et al., 2020;Sadeghi et al., 2023;Sun et al., 2019).The PSR framework is a strategy for choosing and organizing indicators and data based on integration, simplicity, and dynamic response.It is appropriate for establishing health assessment indicators.The PSR framework uses a three-dimensional analysis to understand how people and nature interact.According to, the pressure (P) in the watershed reflects both natural and human activity.New circumstances brought on by stress are referred to as states (S).Response (R) refers to human initiatives, including associated conservation and governance initiatives that try to prevent and lessen the adverse consequences of external pressure on the watershed.Based on the PSR framework, a localized version of the complete assessment index system for health evaluation has been used in this study.
The PSR technique was used to construct the right flood cause and effect concept while considering the impending research's objectives.It was chosen because it was simple to apply, did not need any inaccessible or nonexistent threshold limits for the research variables, and was already well-established in related domains (e.g., Chamani et al., 2023).The variance inflation factor (VIF) test with an upper limit of 10 was used to exclude variables with significant collinearity since there may be collinear correlations among some variables (Sadeghi et al., 2022).The variables were normalized using Equations ( 1) and ( 2) based on the nature and type of effect they had on watershed health after being calculated concerning the indices of PSR of the ecosystem health assessment approach (PSR).This was done to make the quantitative values comparable and eliminate their magnitude effects. (2) In the mentioned relationships, X s , X i , X min , and X max represent the normalized, actual, minimum, and maximum values of the desired criterion, respectively.Then, using the arithmetic mean of the normalized values of the investigated criterion, PSR indices were derived.Due to the high sensitivity to changes in variables, the geometric mean of the PSR indices for each subwatershed was calculated using Equation (3) to determine the ultimate status of watershed health.This allowed information layers to be combined and provided a thorough ecological health index at the watershed scale.
and k are the product of indices and the number of indices, respectively.The Sharghonj Watershed's health index values were classified into five classes (i.e., I, II, III, IV, and V) after determining index values for the PSR ecosystem health assessment framework.Classes, I-V corresponded to healthy and relatively healthy, moderately healthy, relatively unhealthy, and unhealthy watersheds.Additionally, a suitable subclassification was developed to demonstrate the tendency of the governing circumstances following the fluctuation of the health index values in each class (Chamani et al., 2023).Figure 2 shows an overview of the steps and implementation processes of the health and security assessment of the Sharghonj Watershed in Iran.The results of the research were validated based on the extensive field visits and anecdotal shreds of evidence, people's reports, and the current conditions of the region as proposed and employed for such subjective studies by Sadeghi et al. (2008), Najafi et al. (2021), Arantes et al. (2023), andLa Licata et al. (2023).
F I G U R E 2 An overview of the steps and implementation processes of the health and security assessment of the Sharghonj Watershed in South Khorasan Province, Iran.

| Selected criteria and variables
Table 1 lists the factors utilized in the pressure, status, and reaction indices and their impact on subwatersheds.As shown, the variables normalized vegetation cover difference (S 5 ) and the ratio of precipitation to evaporation and transpiration (S 1 ) benefit health from the perspective of flood occurrence.In contrast, other factors employed have a negative impact.To ascertain the variables' independency, the VIF test was performed.This led to categorizing variables with VIF lower than 10 as independent.Since none of the study variables had a VIF more outstanding than 10, all of them were included in the health assessment, as shown in Table 1.Figures 3 and 4 show PSR indices.As can be seen in Figure 3, according to the flood-related pressure index, subwatersheds 11, 16, and 20 are in the moderate class with a positive trend, while subwatersheds 1, 2, 3, 10, 12, and 13 are in the Relatively Low (−) class.Moreover,subwatersheds 4,5,6,7,8,9,14,15,17,21,23,27,28,and 29 in the Relatively Low (+) class and subwatersheds 18, 19, 22, 24, 25, and 26 are placed in the Low (+) class.Also, in the state index, subwatersheds 1 and 2 are in the Moderate (+) class, subwatersheds 3, 4, 5, 6, 8, 10, 11, 12, 14, 15, and 18 are in the Relatively Low (−) class, subwatersheds 7, 9, 13, 16, 17, 19, 20, 21, 22, 23, 26, and 27 5, 10, 11, 12, 13, 14, 20, 23, 26, 27, and 10, 11, 16, 17, 19, 21, 23, 24, 25, and 28 in the Low (+) class and subwatersheds 20 and 29 They are located on the low floor.Table 2 presents the variables with the most influence on pressure, state, response, and health indicators.As can be observed, different factors have distinct effects on the health of subwatersheds.The watershed's mean PSR indices were 0.72, 0.67, and 0.73, respectively.Additionally, the Sharghonj Watershed's weighted mean health and ecological security from the perspective of flood conditions were 0.70 and 0.68, respectively.The watershed is split into two regions, the southeast (mountainous) and northwest (plain), as seen in Figure 1.Due to the high elevation, subwatersheds in the southeast receive the most intense rainfall.Due to this, the factors of maximum 24-h rainfall, depth, and runoff volume are becoming increasingly significant in this part.Additionally, the placement of barberry orchards and residential areas along the banks of rivers in these subwatersheds has had a significant impact on the development of pressures in areas that are vulnerable to flooding, damage from climatic adversity, and damage related to the destruction of barberry orchards and residential areas.As a result of these pressures, several problems in the subwatershed have emerged, with the ratio of orchard and residential lands in the river to the watershed area and the ratio of land with the capacity to cause floods to the watershed area being the most significant.The Sharghonj Watershed has seen a range of responses in different subwatersheds to the pressures and events that have transpired.In this regard, the incidence of different responses has been most influenced by factors 1, 2, and 3.The PSR indices' findings indicate that in 17 subwatersheds, the response index had the most significant impact.The pressure index had the most considerable influence in eight T A B L E 2 Variables (criteria) and indices with the maximum contribution to P, S, and R indices and watershed health status in different subwatersheds of the Sharghonj Watershed, Iran.
subwatersheds, while the state had an enormous effect in three subwatersheds.In the same vein, the applicability of the PSR model to the ecosystem health status of wetlands in West Bengal, India, in 2013-2020 has been successfully reported by Das et al. (2020).The results of this study showed that this area was affected by human pressure, such as population density, urbanization growth rate, and road density, which has led to the destruction of the area and reduced health.Likewise, Hazbavi, Sadeghi, et al. (2020) evaluated the Shazand Watershed in the central Province using the PSR conceptual framework.They claimed that their findings could be understood by managers, planners, and policymakers in the field of natural resources as a reliable and suitable management tool for looking into the problems affecting the country's watersheds.Li et al. (2021) further used the PSR framework to assess the rangeland ecosystem's health in a China region.They also verified the spatial distribution of ecosystem health throughout the study watershed.So, the watershed health decreased from southwest to northeast between 2000 and 2015.In addition, Su et al. (2021) successfully evaluated river health using PSR and M-HSC models in wet and dry seasons.The results showed that both PSR and M-HSC methods showed the same degree of health in the wet season.In contrast, in the dry season, PSR reflects the actual situation better than M-HSC.Also, they verified that PSR is more useful for urban rivers when evaluating the effects of human disturbances on river health.Unlike this, M-HSC is more suitable for rivers in rural areas to evaluate the effects of water protection projects.Furthermore, biological density and the ratio of the number of permitted to non-permitted livestock played a role in the pressure index of 36.54%, according to Ebrahimi Gatgash and Sadeghi (2022) The results showed that the pressure index was the highest among the evaluation indices, and the state index was the lowest.They further noted that the ecological security index identifies the ecological problems of each region more accurately.
The PSR approach and climatological, natural, human, and hydrological factors were used in the current study to assess the health and ecological security of the ecosystems of the Sharghonj Watershed in Birjand City, South Khorasan Province.The current study's findings show that different indicators have varying values in subwatersheds.Based on this, the pressure index varies in different subwatersheds from 0.56 to 0.86, the state from 0.46 to 0.84, and the response from 0.35 to 0.96.Additionally, subwatersheds' mean health and ecological security were separated into 0.53 to 0.83 and 0.27 to 1.01, respectively.As can be implied from the results, various subwatersheds have different conditions reflecting complex dynamic behavior of the affecting factors on watershed health and security, which necessitates watershed-specific and problem-oriented studies.Despite having high health values in some subwatersheds, their ecological security is low, and over time, the possibility of worsening conditions can be expected.On the other hand, the role of each variable is different in the occurrence of floods and the resulting damages in different watersheds.It is, therefore, crucial to pinpoint the critical factors influencing the health of watersheds.Therefore, the best framework for identifying issues and influential factors leading to watershed management will be understanding the challenges and assessing the watershed's health.It can be concluded from the results of the present study that the health assessment is a priority to provide suitable solutions for essential land management; because the continuation of the current situation may cause irreparable damage to the health and security of the watershed.As a result, watershed health and security indicators can be collaboratively used as practical tools in setting priorities and determining watershed status.The watershed health and security assessment is a helpful method for evaluating and identifying effective human, ecological, and environmental resources.Though, further insight research using high-resolution data over a long time series is eventually recommended to reach holistic conclusions.

3. 3 |
Health and ecological security at the subwatershed scaleThe health and ecological security of the Sharghonj Watershed at the subwatershed scale is shown in Figure5.As can be seen, the flood-based health index for subwatershed 2 is in the Moderate (+) class, while subwatersheds 1,3, 10, 11, 12, 16, and 20  fall in the Relatively Low (−) class, subwatersheds4, 5, 6, 8, 9, 13, 14, 15, 17, 23, 26, 27, and 28  are in the Relatively Low (+) class and subwatersheds 7, 18, 19, 21, 22, 24, 25, and 29 are in the Low (+) class.Finally, the F I G U R E 3 Spatial distribution of pressure (P) and state (S) indices in different subwatersheds of the Sharghonj Watershed in South Khorasan Province, Iran.F I G U R E 4 Spatial distribution response (R) index in different subwatersheds of the Sharghonj Watershed in South Khorasan Province, Iran.F I G U R E 5 Health (left) and ecological security (right) atlases in different subwatersheds of the Sharghonj Watershed in South Khorasan Province, Iran.spatial distribution of the ecological security index also shows that subwatershed 1 is in the Moderate (−) class, subwatersheds 4, 5, 6, 14, and 15 are in the Relatively Low (−) class,subwatersheds 3, 8, 9, 12, 13, 18, 22, and 27  in the Relatively Low (+) class, subwatersheds 7, Results of the collinearity test of study variables based on variance inflation factor (VIF) for the Sharghonj Watershed, Iran.
Zhang et al. (2023)3)nalysis to prioritize the Mikhsaz Watershed subwatersheds in Mazandaran Province, Iran.The state and response were governed by hydrological criteria, with 56.07%and 80.11% participation rates, respectively.Since more than 46% of subwatersheds fall into the relatively healthy category, PSR indices were calculated based on this and came out to be 0.68, 0.61, and 0.75.Sadeghi et al. (2022)used the PSR conceptual model framework to prepare the health atlas of the Pishkoh Watershed located in Yazd.The results of the study showed that about 91% and 9% of the watershed are classified as relatively healthy and relatively unhealthy, and also the results of the ecological security index showed that about 41% of the area is classified as relatively unhealthy.Additionally,Zhang et al. (2023)used pressure (P), state (S), and response (R) indices to examine urban ecological resilience.Economic structure (response index), resilience (state index), and morphological resilience (pressure index) were employed in this study to assess resilience.According to the study's findings, morphological and economic resilience performed better than resilience overall in the area under examination.Using the PSR conceptual approach,Sadeghi et al. (2023)analyzed numerous hydrological, human, and climatic elements on health in the Glazchai Watershed.The results showed that the pressure (P), state (S), and response (R) indices contributed 21.66, 33.65, and 44.69%, respectively, to the health index.The range of the watershed health index was 0.53-0.83.A little over 64% of the watershed's surface was in good shape.Additionally, the ecological security index had maximum and minimum values of 1.01 and 0.27, respectively, meaning that 58% of the region has moderate ecological security.Recently,Zhang et al. (2023)conducted a comprehensive assessment of China's ecological security based on the PSR model.