Study on Relationship of Land Cover Changes and Ecohydrological Processes of the Tuul River Basin

Round 1

Reviewer 1 Report

The aim of the paper was investigated  the  annual  average  air  temperature,  total  annual precipitation, annual river discharge variability, and land cover changes at selected stations in the  Tuul  River  Basin. I think that this paper is suitable to main topisc of Sustainability journal and is important for regianal analysis impact of hyman activities on ecohydrology processes in in the  Tuul  River  Basin. At the moment in this work are some  points that should be explain or improving  by Authors

1. In abstract should be mentioned information about impact of resultts on ecohydrological processes in the basin.
2. Intro: Ecohydrology, as sub-discipline of hydrology, deals with the ecological impacts of and interactions with the hydrological cycle. So, chosen ecohydrologic parametersin this study should be linked with aquatic ecosystems. Please expain why were analysed air temperature, precipitation and runoff as representative to ecohydrology analysis? About what ecohydorlogical prosesses is mentioned in manuscript?
3. Methods: Time series of hydrometeorlogic time series are not for the same period like land cover changes. Landcover changes taken from only 10 years period. So I am not sure if conclustions about influence of land cover on hydrometeorologic time series can be appriopriate and explain variability of the time series.
4. Fig 3 - 5: please add title of x, y axis
5. Table 2 and 3: please explain what do signs means? Statistical significace level?
6. Ch 3.3: I think that is too short period of land cover to explain trends of air, precipitation and runoff. I think that analysis seasonal hydrometeorological parameters would be better than annual values because some inter annual relationships woiuld be visible. Please Authors about opinion and possibility of caclulation of hydrometeorologic parameters not only for annual but for seasonal or monthly time resolution
7. Fig 8: please add information about statistical significance of correlation coefficient
8. Conclusion L321-322: too risk sentence because land cover was analysed only for 10 years   

Author Response

-------------------------------------- Reviewer -1----------------------------------------

1. Review Report Form-1

The aim of the paper was investigated the annual average air temperature, total annual precipitation, annual river discharge variability, and land cover changes at selected stations in the  Tuul  River  Basin. I think that this paper is suitable to main topisc of Sustainability journal and is important for regianal analysis impact of hyman activities on ecohydrology processes in in the  Tuul  River  Basin. At the moment in this work are some points that should be explain or improving by Authors

1. Comment [1- Reviewer -1]:

In abstract should be mentioned information about impact of resultts on ecohydrological processes in the basin.

Response: Done.  Line: 39-45.

During the study period, changes in land cover were directly related to hydrometeorological main parameters. Between 2000 and 2020, the amount of grassland decreased by 319.67 km², while the amount of water bodies land increased by 28.36 km². In the study area were changed mainly water bodies and sensitive areas of the landcover types due to changes in precipitation. Studies in the arid and semi-arid regions of Central Asia show that ecohydrological processes change has a significant impact on land cover changes.

2. Comment [2- Reviewer -1]:

Intro: Ecohydrology, as sub-discipline of hydrology, deals with the ecological impacts of and interactions with the hydrological cycle. So, chosen ecohydrologic parametersin this study should be linked with aquatic ecosystems. Please expain why were analysed air temperature, precipitation and runoff as representative to ecohydrology analysis? About what ecohydorlogical prosesses is mentioned in manuscript?

Response: Done.  Line: 75-83.

Therefore, it may be useful to consider the relationship between hydrometeorology factors (air temperature, precipitation, river discharge) and changes in land cover from the natural factors that influence the ecohydrological process. On the one hand, it can be an effective basis for identifying direct and indirect ecological impacts of ecohydrological processes on plants, animals, soil cover, and public health [13,14].

On the other hand, it is important to determine the sensitivity (increase and decrease) of water contingents for water bodies, wetland, and permanent snow and ice of the land cover in the river basin. In other words, it has many benefits, such as determining how some ecohydrological parameter changes affect surface aquifers and detecting direct and indirect effects [15,16].

3. Comment [3- Reviewer -1]:

Methods: Time series of hydrometeorlogic time series are not for the same period like land cover changes. Landcover changes taken from only 10 years period. So I am not sure if conclustions about influence of land cover on hydrometeorologic time series can be appriopriate and explain variability of the time series.

Response: Done. Line: 114-117.

Different trends in hydrometeorology variables (1979-2019) and landcover changes (2000, 2010, and 2020) were determined and relationships using the Innovative trend analysis method, Mann-Kendall test, and Sen's slope estimator method, satellite imagery and calculated the correlation.

Response: Done. Line: 250-266.

The maximum-likelihood classification of the Tuul River Basin was used to land cover maps in three different periods (2000, 2010, and 2020). To confirm this, it was compared with the soil map, topographic map, ecological landscape potential map, vegetation map, and forest map. With appreciable accuracy, the Tuul river basin landscape was classified according to eight land classes (Figure 7).

Figure 7. Land cover classification map in the Tuul River Basin.

The number of classified pixels varied greatly in several types of land cover. It is noteworthy that most of the maximum changes occurred in the grassland and wetland area from 2000 to 2010. During these 10 years, the grassland area and wetland have increased by 59.00 km² and 11.89 km². In contrast, the water bodies and cultivated lands have decreased by 45.89 km² and 28.00 km². However, the change in land cover was even greater between 2010 and 2020, which was almost the opposite of the previous decade. In other words, the amount of Grassland significantly decreased by -378.67 km² during study period, while the number of Water bodies increased by 74.25 km² (Table 4).

Table 4. Land cover type and changed area

There has also been a sharp increase in the size of the Bareland, which has not been evident in the previous decade. In this case, the high variability of the land cover indicates that there are some factors that strongly influence it (Figure 9b and 9c).  

Response: Done. Line: 284-299.

From 2000 to 2020, the forms of land cover that are most sensitive to temperature and water have changed significantly (Table 6).

Table 6. Transformation-matrix of land covers from 2000 to 2020 (km²)

From 2000 to 2020, about 5.13 km² area of artificial surfaces land has been converted into grassland. The conversion of cultivated land to artificial surfaces land, grassland, and shrubland was 2.77 km², 292.95 km², and 3.57 km², respectively. The conversion of forest land to bareland, grassland, water bodies, and wetland was 2.19 km², 438.02 km², 4.02 km², and 3.71 km², respectively. The conversion of grassland to artificial surfaces land, bareland, cultivated land, forest land, shrubland, water bodies, and wetland was 96.63 km², 31.93 km², 79.02 km², 557.73 km², 2531.30 km², 62.13 km² and 14.03 km², respectively. The conversion of shrubland to artificial surfaces land, bareland, cultivated land, grassland, water bodies, and wetland was 8.70 km², 70.48 km², 1.19 km², 2177.62 km², 13.91 km² and 1.11 km², respectively. The conversion of water bodies to forest land, grassland, shrubland, and wetland was 4.08 km², 36.55 km², 9.29 km², and 2.26 km² respectively. The conversion of wetland to grassland, shrubland, and water bodies, were 3.59 km², 4.09 km², and 1.55 km², respectively.

4. Comment [4- Reviewer -1]:

Fig 3 - 5: please add title of x, y axis

Response: Done. Line: 139-142.

 My opinion: Adding the X and Y axes to each figure makes it difficult to see, so it is included in “Figure 3” in the methodological section.

Mark the first half of the time series sorted along the () axis and the second half of the time series along the () axis (Figure 3).

Figure 3. Image structure of the Innovative trend analysis method..

5. Comment [5- Reviewer -1]:

Table 2 and 3: please explain what do signs means? Statistical significace level?

Response: Done.  Line: 214, 229, 246.

* Trends at 0.1 significance level; ** Trends at 0.05 significance level; *** Trends at 0.01 significance level.

6. Comment [6- Reviewer -1]:

Ch 3.3: I think that is too short period of land cover to explain trends of air, precipitation and runoff. I think that analysis seasonal hydrometeorological parameters would be better than annual values because some inter annual relationships woiuld be visible. Please Authors about opinion and possibility of caclulation of hydrometeorologic parameters not only for annual but for seasonal or monthly time resolution

Response: Done.  Line: 327-349

Therefore, this may have had a significant impact on reducing the water bodies (45.89 km²) land surface area of the Tuul River Basin from 2000 to 2010 (Table 4). However, between 2010 and 2020, a slight increase in precipitation in the basin increased the area with water bodies (74.25 km²). Between 2000 and 2020, the amount of grassland decreased by 319.67 km², while the amount of water bodies land increased by 28.36 km². And also, due to temperature and evaporation, the amount of grassland area decreased and the amount of bareland increased. Therefore, it is important to establish an interrelationship by comparing the main parameters of the hydrometeorological, which have a major impact on the ecohydrological process, with water bodies and sensitive areas of the landcover types (Figure 9).

Figure 9. Interrelationships between precipitation and land cover in the Tuul River Basin between 2000 and 2020. a) changes in precipitation, b) changes in land cover between 2000 and 2010, and c) changes in land cover from 2010 to 2020.

Studies in the arid and semi-arid regions of Central Asia show that climate change has a significant impact on land cover changes [5,42]. When linking changes and shifts in this land cover to a hydrological system, it may be important to consider the spatial and temporal interrelationships of the key factors that affect it. In addition, changes in land cover have occurred in basin areas as a result of human and natural impacts (Figure 10).

Figure 10. Land cover changes of the Tuul river basin in 2000 - 2020.

The most changed areas were along the river zone area. In particular, the size of grasslands along the river basin has changed significantly and shifted to other forms. There is also a not less of change in cultivated land and artificial surfaces that are being changed by human activities.

7. Comment [7- Reviewer -1]:

Fig 8: please add information about the statistical significance of correlation coefficient

Response: Done. Line: 317-319.

It was observed that the average annual precipitation has a strong positive, statistically significant correlation with river water discharge (r = 0.70).

8. Comment [8- Reviewer -1]:

Conclusion L321-322: too risk sentence because land cover was analysed only for 10 years   

Response: Done.  Line: 374-386.

Changes in landcover varied in relation to hydrometeorological changes. It is noteworthy that most of the maximum changes occurred in the grassland and wetland area from 2000 to 2010. During these 10 years, the grassland area and wetland have increased by 59.00 km² and 11.89 km². In contrast, the water bodies and cultivated lands have decreased by 45.89 km² and 28.00 km². However, the change in land cover was even greater between 2010 and 2020, which was almost the opposite of the previous decade. In other words, the amount of Grassland significantly decreased by -378.67 km² during the study period, while the number of Water bodies increased by 74.25 km². Between 2000 and 2020, the amount of grassland decreased by 319.67 km², while the amount of water bodies land increased by 28.36 km². During the study period, changes in land cover were directly related to hydrometeorological main parameters. Water bodies and sensitive areas of the landcover types have changed, mainly due to changes in precipitation in the study area. Studies in the arid and semi-arid regions of Central Asia show that climate change has a significant impact on land cover changes.

Author Response File: Author Response.pdf

Reviewer 2 Report

Relating land cover changes with eco-hydrological processes in a river basin is an interesting study. The abstract, converse to the title, does not say a lot about land cover responses. Also, in the discussion section (3.3) I tried to find any ecological level discussion but it lacks almost complete, but the authors seem to discuss here relationships with ecohydrological processes, they are rather hydrological only. 

line 38. what does phi represent here? please mention.

Overall, the ms is well written with good use of language (grammar, syntax, redaction) and can be considered for publication.

Author Response

---------------------------------------- Reviewer -2--------------------------------------

2. Review Report Form-2

Comments and Suggestions for Authors

1. 1. Comment [1- Reviewer -2]:

Relating land cover changes with eco-hydrological processes in a river basin is an interesting study. The abstract, converse to the title, does not say a lot about land cover responses.

Response: Done.  Line: 39-45.

During the study period, changes in land cover were directly related to hydrometeorological main parameters. Between 2000 and 2020, the amount of grassland decreased by 319.67 km², while the amount of water bodies land increased by 28.36 km². In the study area were changed mainly water bodies and sensitive areas of the landcover types due to changes in precipitation. Studies in the arid and semi-arid regions of Central Asia show that ecohydrological processes change has a significant impact on land cover changes.

2. 2. Comment [2- Reviewer -2]:

Also, in the discussion section (3.3) I tried to find any ecological level discussion but it lacks almost complete, but the authors seem to discuss here relationships with ecohydrological processes, they are rather hydrological only.

Response: Done.  Line: 327-349

Therefore, this may have had a significant impact on reducing the water bodies (45.89 km²) land surface area of the Tuul River Basin from 2000 to 2010 (Table 4). However, between 2010 and 2020, a slight increase in precipitation in the basin increased the area with water bodies (74.25 km²). Between 2000 and 2020, the amount of grassland decreased by 319.67 km², while the amount of water bodies land increased by 28.36 km². And also, due to temperature and evaporation, the amount of grassland area decreased and the amount of bareland increased. Therefore, it is important to establish an interrelationship by comparing the main parameters of the hydrometeorological, which have a major impact on the ecohydrological process, with water bodies and sensitive areas of the landcover types (Figure 9).

Figure 9. Interrelationships between precipitation and land cover in the Tuul River Basin between 2000 and 2020. a) changes in precipitation, b) changes in land cover between 2000 and 2010, and c) changes in land cover from 2010 to 2020.

Studies in the arid and semi-arid regions of Central Asia show that climate change has a significant impact on land cover changes [5,42]. When linking changes and shifts in this land cover to a hydrological system, it may be important to consider the spatial and temporal interrelationships of the key factors that affect it. In addition, changes in land cover have occurred in basin areas as a result of human and natural impacts (Figure 10).

Figure 10. Land cover changes of the Tuul river basin in 2000 - 2020.

The most changed areas were along the river zone area. In particular, the size of grasslands along the river basin has changed significantly and shifted to other forms. There is also a not less of change in cultivated land and artificial surfaces that are being changed by human activities.

3. 3. Comment [3- Reviewer -2]:

line 38. what does phi represent here? please mention.

Response: Done.  Line: 37.

River discharge a significant decreasing trend was observed in Terelj (ф = − 2.72), Ulaanbaatar (ф = − 5.63) stations, whereas in the other Altanbulag, Lun, and Orkhontuul stations demonstrated a significant increasing trend.

4. 4. Comment [4- Reviewer -2]:

Overall, the ms is well written with good use of language (grammar, syntax, redaction) and can be considered for publication.

Response: Done. Thank you very much. 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Thank you for improving paper according to my suggestions. I feel that current version of a paper is much better than previous.