*3.1. The Proportion of Cultivated Land in the Beach Area*

The statistics from the Third National Land Survey indicated that a large proportion of the Yellow River beach area was cultivated land. Cultivated land, garden land and other agricultural land accounted for 66.04% of the total beach area. Among them, cultivated land accounted for the largest proportion (58.26%) and covered an area of 1557.19 km<sup>2</sup> (Figure 5). Irrigable land, paddy field and dry land accounted for 97% and 3% of the cultivated land, respectively. *Water* **2022**, *14*, x FOR PEER REVIEW 8 of 15


**Figure 5.** Area proportion of various land use types in the Yellow River beach in 2020.

**Figure 5.** Area proportion of various land use types in the Yellow River beach in 2020. The cultivated land was unevenly distributed through the counties and cities of the Yellow River beach area (Figure 6). To reflect cultivated land information more clearly, five areas were randomly selected and magnified, the same areas were magnified in the figures below. Xinxiang, Puyang and Jiaozuo cities accounted for 73.13% of the cultivated land in the beach area. Xinxiang, with 41.84%, had the largest area of cultivated land in The area of dry land accounted for 2.20% of the cultivated land, which was unevenly distributed between the north and south banks of the Yellow River, counties and cities along the Yellow River beach were shown in Figure 5. Of the dry land, 82.84% distributed throughout seven counties on the south bank and 17.16% distributed through six counties on the north bank. Gongyi county had the largest area of dry land (9.95 km<sup>2</sup> ), followed by Xiangfu district (8.68 km<sup>2</sup> ). Six counties, including Lankao, Puyang, Longting, Mengzhou and Wuzhi, had no areas of dry land.

and 66.01% of the paddy field total in the beach area (Figure 7).

irrigable land in the beach area. The cities with a large area of dry land were Zhengzhou, Kaifeng and Luoyang, the counties with large dry land areas were Gongyi, Mengjin and Xiangfu district. Gongyi county had a dry land area of 9.95 km2, which accounted for 0.05% of the cultivated land area in Zhengzhou city and 28.90% of the total dry land in the beach area. Luoyang, Kaifeng and Puyang cities had the largest area of paddy field, with the largest area in Mengjin and Lankao counties. Paddy field in Mengjin county covered an area of 6.39 km2, which accounted for 21.74% of the cultivated land in Luoyang city

the beach area, across 651.57 km2. Puyang followed, with 18.14% of the total cultivated land area across 282.40 km2. Jiaozuo had 13.15% of the cultivated land area, across 204.80 km2. The counties with a large area of cultivated land were Yuanyang and Changyuan. Xinxiang and Jiaozuo cities had a large area of irrigable land, and Yuanyang, Changyuan

The cultivated land was unevenly distributed through the counties and cities of the Yellow River beach area (Figure 6). To reflect cultivated land information more clearly, five areas were randomly selected and magnified, the same areas were magnified in the figures below. Xinxiang, Puyang and Jiaozuo cities accounted for 73.13% of the cultivated land in the beach area. Xinxiang, with 41.84%, had the largest area of cultivated land in the beach area, across 651.57 km<sup>2</sup> . Puyang followed, with 18.14% of the total cultivated land area across 282.40 km<sup>2</sup> . Jiaozuo had 13.15% of the cultivated land area, across 204.80 km<sup>2</sup> . The counties with a large area of cultivated land were Yuanyang and Changyuan. Xinxiang and Jiaozuo cities had a large area of irrigable land, and Yuanyang, Changyuan were counties with large irrigable land area, Yuanyang, with an area of 275.76 km<sup>2</sup> , accounted for 42.32% of the cultivated land area in Xinxiang city and 18.21% of the total irrigable land in the beach area. The cities with a large area of dry land were Zhengzhou, Kaifeng and Luoyang, the counties with large dry land areas were Gongyi, Mengjin and Xiangfu district. Gongyi county had a dry land area of 9.95 km<sup>2</sup> , which accounted for 0.05% of the cultivated land area in Zhengzhou city and 28.90% of the total dry land in the beach area. Luoyang, Kaifeng and Puyang cities had the largest area of paddy field, with the largest area in Mengjin and Lankao counties. Paddy field in Mengjin county covered an area of 6.39 km<sup>2</sup> , which accounted for 21.74% of the cultivated land in Luoyang city and 66.01% of the paddy field total in the beach area (Figure 7). *Water* **2022**, *14*, x FOR PEER REVIEW 9 of 15

**Figure 6.** Distribution of cultivated land in the Yellow River beach in 2020. **Figure 6.** Distribution of cultivated land in the Yellow River beach in 2020.

**Figure 7.** Distribution of the cultivated areas in each county in the Yellow River beach in 2020.

During the study period, continuous beach land covered an area of 1630.92 km2,

scattered across 18,243 patches, and accounted for 61.02% of the total area in the Yellow River beach (Table 2). None of these patches were inundated by water over the 34 years. There were 29 continuous beach patches ≥1.0 km2, which covered an area of 1544.29 km2 and accounted for 94.68% of the continuous beach land area. Most of these patches were in Xinxiang (nine patches), Zhengzhou (seven patches) and Puyang (six patches) cities; there were 10 continuous beach patches ≥ 10.0 km2, which covered an area of 1492.11 km2 and accounted for 91.49% of the continuous beach land area, mainly in Zhengzhou (three patches), Xinxiang (two patches) and Puyang (two patches) cities; and there were 151 patches with continuous beach land areas ≥0.1 km2, which covered an area of 1577.66 km2,

*3.2. The Distribution of Continuous Beach Land* 

**Figure 6.** Distribution of cultivated land in the Yellow River beach in 2020.

**Figure 7.** Distribution of the cultivated areas in each county in the Yellow River beach in 2020. **Figure 7.** Distribution of the cultivated areas in each county in the Yellow River beach in 2020.

#### *3.2. The Distribution of Continuous Beach Land*

*3.2. The Distribution of Continuous Beach Land*  During the study period, continuous beach land covered an area of 1630.92 km2, scattered across 18,243 patches, and accounted for 61.02% of the total area in the Yellow River beach (Table 2). None of these patches were inundated by water over the 34 years. There were 29 continuous beach patches ≥1.0 km2, which covered an area of 1544.29 km2 and accounted for 94.68% of the continuous beach land area. Most of these patches were in Xinxiang (nine patches), Zhengzhou (seven patches) and Puyang (six patches) cities; there were 10 continuous beach patches ≥ 10.0 km2, which covered an area of 1492.11 km2 and accounted for 91.49% of the continuous beach land area, mainly in Zhengzhou (three patches), Xinxiang (two patches) and Puyang (two patches) cities; and there were 151 patches with continuous beach land areas ≥0.1 km2, which covered an area of 1577.66 km2, During the study period, continuous beach land covered an area of 1630.92 km<sup>2</sup> , scattered across 18,243 patches, and accounted for 61.02% of the total area in the Yellow River beach (Table 2). None of these patches were inundated by water over the 34 years. There were 29 continuous beach patches <sup>≥</sup>1.0 km<sup>2</sup> , which covered an area of 1544.29 km<sup>2</sup> and accounted for 94.68% of the continuous beach land area. Most of these patches were in Xinxiang (nine patches), Zhengzhou (seven patches) and Puyang (six patches) cities; there were 10 continuous beach patches <sup>≥</sup> 10.0 km<sup>2</sup> , which covered an area of 1492.11 km<sup>2</sup> and accounted for 91.49% of the continuous beach land area, mainly in Zhengzhou (three patches), Xinxiang (two patches) and Puyang (two patches) cities; and there were 151 patches with continuous beach land areas <sup>≥</sup>0.1 km<sup>2</sup> , which covered an area of 1577.66 km<sup>2</sup> , and accounted for 96.73% of the continuous beach land area; there were 18,085 continuous beach patches <sup>≤</sup>0.1 km<sup>2</sup> , scattered across the beach area of numerous cities. Xinxiang was the prefecture-level city with the largest continuous beach land area, followed by Puyang and Jiaozuo cities, ranking second and third, respectively.

**Table 2.** The number of continuous beach land patches in the Yellow River beach in 2020.


There was a gap in the distribution of continuous beach land on the left bank, right bank and coastal cities in the Yellow River beach. The continuous beach land area covered 1260.09 km<sup>2</sup> on the left bank in the Yellow River beach and 370.89 km<sup>2</sup> on the right bank. The 34 years' continuous beach land areas were mainly distributed in Xinxiang, Puyang, Jiaozuo and other cities on the left bank of the Yellow River. The continuous beach land area in Xinxiang, Puyang and Jiaozuo cities accounted for 43.94%, 18.83% and 14.49% of

the total continuous beach land, respectively. Luoyang city (29.60 km<sup>2</sup> ) accounted for only 1.81% of the total continuous beach land in the Yellow River beach area. the total continuous beach land, respectively. Luoyang city (29.60 km2) accounted for only 1.81% of the total continuous beach land in the Yellow River beach area.

and accounted for 96.73% of the continuous beach land area; there were 18,085 continuous beach patches ≤0.1 km2, scattered across the beach area of numerous cities. Xinxiang was the prefecture-level city with the largest continuous beach land area, followed by Puyang

 **Luoyang Jiaozuo Zhengzhou Xinxiang Kaifang Puyang Summary** 

There was a gap in the distribution of continuous beach land on the left bank, right bank and coastal cities in the Yellow River beach. The continuous beach land area covered 1260.09 km2 on the left bank in the Yellow River beach and 370.89 km2 on the right bank. The 34 years' continuous beach land areas were mainly distributed in Xinxiang, Puyang, Jiaozuo and other cities on the left bank of the Yellow River. The continuous beach land area in Xinxiang, Puyang and Jiaozuo cities accounted for 43.94%, 18.83% and 14.49% of

**Table 2.** The number of continuous beach land patches in the Yellow River beach in 2020.

≥0.1 km2 8 9 28 50 38 18 151 ≥1.0 km2 3 2 7 9 2 6 29 ≥10.0 km2 1 1 3 2 1 2 10

#### *3.3. Proportion of the Cultivated Land for the Staple Crops 3.3. Proportion of the Cultivated Land for the Staple Crops*

*Water* **2022**, *14*, x FOR PEER REVIEW 10 of 15

and Jiaozuo cities, ranking second and third, respectively.

Winter wheat and summer corn was the staple crops grown on the cultivated land in the Yellow River beach. Winter wheat covered a larger area than summer corn. Winter wheat covered 1126.94 km<sup>2</sup> and accounted for 72.37% of the total cultivated land (Figure 8). The harvested area of winter wheat covered 1063.95 km<sup>2</sup> and accounted for 94.44% of the cultivated area of winter wheat and 68.32% of the cultivated land. The area of summer corn covered 1059.30 km<sup>2</sup> and accounted for 68.03% of the total cultivated land (Figure 9). The harvested area of summer corn was 1010.89 km<sup>2</sup> and accounted for 95.43% of the cultivated area of summer corn and 64.92% of the cultivated land. Winter wheat and summer corn was the staple crops grown on the cultivated land in the Yellow River beach. Winter wheat covered a larger area than summer corn. Winter wheat covered 1126.94 km2 and accounted for 72.37% of the total cultivated land (Figure 8). The harvested area of winter wheat covered 1063.95 km2 and accounted for 94.44% of the cultivated area of winter wheat and 68.32% of the cultivated land. The area of summer corn covered 1059.30 km2 and accounted for 68.03% of the total cultivated land (Figure 9). The harvested area of summer corn was 1010.89 km2 and accounted for 95.43% of the cultivated area of summer corn and 64.92% of the cultivated land.

**Figure 8. Figure 8.**  Distribution of winter wheat in the Yellow River beach in 2020. Distribution of winter wheat in the Yellow River beach in 2020.

**Figure 9.** Distribution of summer corn in the Yellow River beach in 2020. **Figure 9.** Distribution of summer corn in the Yellow River beach in 2020.

The area of winter wheat and summer corn varied between the counties and cities

532.87 km2, accounted for 47.29% of the total winter wheat area in the beach area, followed by Puyang and Jiaozuo cities, which accounted for 18.69% and 13.37% of the total winter wheat area, respectively. Luoyang had 15.22 km2, which was the smallest area of winter wheat and accounted for 1.35% of the total winter wheat area in the beach area. The counties statistics (Figure 11) indicated that Yuanyang and Changyuan had a large area of winter wheat. Yuanyang, with 225.20 km2, accounted for 19.98% of the total winter wheat area in the beach area, while Changyuan accounted for 16.91% of the total winter wheat area. Jinshui district in Zhengzhou city had only 0.3 km2, which was the smallest area of winter wheat. Xinxiang city had the largest area of summer corn (Figure 10), which covered 475.82 km2 and accounted for 44.92% of the total summer corn area in the beach area. Puyang and Kaifeng cities followed, with 16.93% and 13.01% of the total summer corn area, respectively. Luoyang city had the smallest area of summer corn, with only 15.22 km2 or 1.35% of the total summer corn grown in the beach area. The counties statistics (Figure 11) indicated that the summer corn areas were relatively large in Yuanyang, Changyuan, and Fengqiu, with Yuanyang (203.8 km2), Changyuan and Fengqiu counties accounting for 19.24%, 17.11% and 11.24%, of the total summer corn grown in the beach area, respectively. Jinshui district in Zhengzhou city, with only 0.79

km2, had the smallest area of summer corn.

The area of winter wheat and summer corn varied between the counties and cities (Figure 10). The city with the largest winter wheat area was Xinxiang, with an area of 532.87 km<sup>2</sup> , accounted for 47.29% of the total winter wheat area in the beach area, followed by Puyang and Jiaozuo cities, which accounted for 18.69% and 13.37% of the total winter wheat area, respectively. Luoyang had 15.22 km<sup>2</sup> , which was the smallest area of winter wheat and accounted for 1.35% of the total winter wheat area in the beach area. The counties statistics (Figure 11) indicated that Yuanyang and Changyuan had a large area of winter wheat. Yuanyang, with 225.20 km<sup>2</sup> , accounted for 19.98% of the total winter wheat area in the beach area, while Changyuan accounted for 16.91% of the total winter wheat area. Jinshui district in Zhengzhou city had only 0.3 km<sup>2</sup> , which was the smallest area of winter wheat. Xinxiang city had the largest area of summer corn (Figure 10), which covered 475.82 km<sup>2</sup> and accounted for 44.92% of the total summer corn area in the beach area. Puyang and Kaifeng cities followed, with 16.93% and 13.01% of the total summer corn area, respectively. Luoyang city had the smallest area of summer corn, with only 15.22 km<sup>2</sup> or 1.35% of the total summer corn grown in the beach area. The counties statistics (Figure 11) indicated that the summer corn areas were relatively large in Yuanyang, Changyuan, and Fengqiu, with Yuanyang (203.8 km<sup>2</sup> ), Changyuan and Fengqiu counties accounting for 19.24%, 17.11% and 11.24%, of the total summer corn grown in the beach area, respectively. Jinshui district in Zhengzhou city, with only 0.79 km<sup>2</sup> , had the smallest area of summer corn. The area of winter wheat and summer corn varied between the counties and cities (Figure 10). The city with the largest winter wheat area was Xinxiang, with an area of 532.87 km2, accounted for 47.29% of the total winter wheat area in the beach area, followed by Puyang and Jiaozuo cities, which accounted for 18.69% and 13.37% of the total winter wheat area, respectively. Luoyang had 15.22 km2, which was the smallest area of winter wheat and accounted for 1.35% of the total winter wheat area in the beach area. The counties statistics (Figure 11) indicated that Yuanyang and Changyuan had a large area of winter wheat. Yuanyang, with 225.20 km2, accounted for 19.98% of the total winter wheat area in the beach area, while Changyuan accounted for 16.91% of the total winter wheat area. Jinshui district in Zhengzhou city had only 0.3 km2, which was the smallest area of winter wheat. Xinxiang city had the largest area of summer corn (Figure 10), which covered 475.82 km2 and accounted for 44.92% of the total summer corn area in the beach area. Puyang and Kaifeng cities followed, with 16.93% and 13.01% of the total summer corn area, respectively. Luoyang city had the smallest area of summer corn, with only 15.22 km2 or 1.35% of the total summer corn grown in the beach area. The counties statistics (Figure 11) indicated that the summer corn areas were relatively large in Yuanyang, Changyuan, and Fengqiu, with Yuanyang (203.8 km2), Changyuan and Fengqiu counties accounting for 19.24%, 17.11% and 11.24%, of the total summer corn grown in the beach area, respectively. Jinshui district in Zhengzhou city, with only 0.79 km2, had the smallest area of summer corn.

*Water* **2022**, *14*, x FOR PEER REVIEW 11 of 15

**Figure 9.** Distribution of summer corn in the Yellow River beach in 2020.

**Figure 10.** Distribution of crops in each city in the Yellow River beach in 2020. **Figure 10.** Distribution of crops in each city in the Yellow River beach in 2020.

**Figure 11.** Distribution of crops in each county in the Yellow River beach in 2020. **Figure 11.** Distribution of crops in each county in the Yellow River beach in 2020.

land resources in beach areas. In the continuous beach land, the cultivated land occupied a relatively high area proportion. Consistent with previous studies, grain production was a major land use in the Yellow River beach area. However, it is worth noting that there are beach lands that have been waterless for many years, and these beach lands have been developed into cultivated land resources. These cultivated land resource need to be protected in terms of ensuring food security for the million people in the Yellow River beach area or even at Henan province [54]. However, the extent of the cultivated land resources in the beach area cannot be expanded infinitely. Cultivated land accounts for a large area proportion in the whole beach area, while other land use types such as wetlands cover relatively small areas correspondingly. Optimizing and adjusting the ratio of cultivated land to ecologically protected land is essential to regional balance, secure land (Sustaina-

The Yellow River beach area was dominated by agriculture, and the construction of agricultural infrastructure should be strengthened to enrich the types of crops. As showed by this study, the agricultural planting types in this area were mainly winter wheat, summer corn. The fact that the crops have a single structure and few crop types are not conducive to future development. The single structure of agricultural production does not adapt to the diversity of natural resources, and it is greatly affected by market price fluctuations [55]. However, given that the beach area has benefited from a large irrigation project (the Yellow River Diversion Irrigation Project), the agricultural output is relatively high and the harvest area of both winter wheat and summer corn all exceeds 94% indicat-

Rapid socio-economic development in the past decades has increased the consumption of water and land resources, leading to negative impacts and making the ecological environment of the Yellow River beach area very fragile [56–58]. However, due to the narrow span of the left and right banks of the Yellow River, although this study has preliminary discussed the spatial-temporal dynamics of water and land resources, it is still insufficient to study the fragile ecological environment. Generally speaking, as the channel of flood discharge, there should be more wetland in the beach area [59,60]. According to our finding, there are large continuous lands without water body historically in the beach area. These beaches are suitable for cultivating and some of them have been developed into cultivated land, which contributes to the food security in the region. Regardless of whether it is based on the national Yellow River protection strategy or according to our

ble Development Goals 15), and ensuring food security.

ing the importance of advanced irrigation facilities.

**4. Discussion** 

#### **4. Discussion**

It is important to strengthen the monitoring and utilization of agricultural cultivated land resources in beach areas. In the continuous beach land, the cultivated land occupied a relatively high area proportion. Consistent with previous studies, grain production was a major land use in the Yellow River beach area. However, it is worth noting that there are beach lands that have been waterless for many years, and these beach lands have been developed into cultivated land resources. These cultivated land resource need to be protected in terms of ensuring food security for the million people in the Yellow River beach area or even at Henan province [54]. However, the extent of the cultivated land resources in the beach area cannot be expanded infinitely. Cultivated land accounts for a large area proportion in the whole beach area, while other land use types such as wetlands cover relatively small areas correspondingly. Optimizing and adjusting the ratio of cultivated land to ecologically protected land is essential to regional balance, secure land (Sustainable Development Goals 15), and ensuring food security.

The Yellow River beach area was dominated by agriculture, and the construction of agricultural infrastructure should be strengthened to enrich the types of crops. As showed by this study, the agricultural planting types in this area were mainly winter wheat, summer corn. The fact that the crops have a single structure and few crop types are not conducive to future development. The single structure of agricultural production does not adapt to the diversity of natural resources, and it is greatly affected by market price fluctuations [55]. However, given that the beach area has benefited from a large irrigation project (the Yellow River Diversion Irrigation Project), the agricultural output is relatively high and the harvest area of both winter wheat and summer corn all exceeds 94% indicating the importance of advanced irrigation facilities.

Rapid socio-economic development in the past decades has increased the consumption of water and land resources, leading to negative impacts and making the ecological environment of the Yellow River beach area very fragile [56–58]. However, due to the narrow span of the left and right banks of the Yellow River, although this study has preliminary discussed the spatial-temporal dynamics of water and land resources, it is still insufficient to study the fragile ecological environment. Generally speaking, as the channel of flood discharge, there should be more wetland in the beach area [59,60]. According to our finding, there are large continuous lands without water body historically in the beach area. These beaches are suitable for cultivating and some of them have been developed into cultivated land, which contributes to the food security in the region. Regardless of whether it is based on the national Yellow River protection strategy or according to our study results, the cultivated land resources in the beach area are already relatively large and "we should not stop eating because of choking", namely, blindly pursue the expansion of ecological protected area and neglect the original farming resources and suitable farming environment. Therefore, the beach area should have a fine strategy that protects the cultivated land and ecological land resources and promotes the development of agriculture rather than extensive development. While protecting the ecological environment, it is necessary to combine the actual conditions of the residents in the beach area to ensure the sustainable development of agriculture and practice the national strategy of ecological protection and high-quality development of the Yellow River basin.

By combining water extraction methods and the Third National Land Survey data, this study accurately measured the area of water body and cultivated land. However, this study was not able to comprehensively explore the factors influencing the pattern of continuous beach land and staple crops in the Yellow River beach area. In future, more attention should be paid to the reason analysis.

#### **5. Conclusions**

The beach area along the floodplains of the middle and lower reaches of the Yellow River comprises valuable cultivated land resources. Based on the Third National Land Survey data and remote sensing images. This study analyzed the spatial and temporal

changes of continuous beach land and cultivated land. Our study revealed that cultivated land occupied a large area of the total beach area (1557.19 km<sup>2</sup> ) and most of the beach area was covered by continuous beach area (61.02%). Patch area of the continuous beach area that more than 0.1 km<sup>2</sup> accounted for 96.73% of the total area of continuous beach lands, which provides numerous land resources for cultivating. The staple crops in the Yellow River beach area were winter wheat and summer corn. Winter wheat and summer corn accounted for 72.37% and 68.03% of the total cultivated land, respectively. which implies that the beach area plays an important role in ensuring regional food security for millions of people living in the study area. When protecting the ecological environment in the beach area, the cultivated land should be protected too.

**Author Contributions:** Conceptualization, Y.R., Y.C., and M.L.; methodology, Y.R.; software, Y.R., Z.S., Q.L. and M.L.; formal analysis, Y.Q., and Q.L.; writing-original draft preparation, Q.L., Z.S.; writing-review and editing, Y.C., Y.Q.; supervision, Y.Q., Y.C.; funding acquisition, Y.Q., Y.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by National Key Research and Development Program of China [2021YFE0106700], National Natural Science Foundation of China [42071415], Outstanding Youth Science Foundation Project of Natural Science Foundation of Henan province [202300410049], Key Laboratory of Land Surface Pattern and Simulation, Chinese Academy of Sciences [LB2021006], and Special project of natural resources development in Henan province (Ecological product value and Ecological carbon sink).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Landsat image from Google Earth Engine (GEE) (https://earthengine. google.org/ accessed on 9 September 2021), and water data processing in the GEE. Sentinel L1C data is downloaded from ESA (https://scihub.copernicus.eu/ accessed on 29 November 2021).

**Acknowledgments:** Thanks to Henan Provincial Department of Natural Resources for the support of this research data, thanks to Leonie Seabrook for the detailed revision of this paper.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

