📚 A-Level CCEA Geography: Formula and Theorem Quick Reference Handbook | A-Level CCEA 地理：公式定理速查手册
This quick reference handbook compiles essential formulas, models, and statistical techniques required for the CCEA A-Level Geography specification. It covers physical geography calculations such as river discharge, humidity, and soil moisture, alongside human geography metrics including population change, dependency ratios, urbanisation, and inequality measures. Fieldwork statistical tests like Spearman’s rank correlation and standard deviation are also included to support your investigation skills.
本速查手册汇编了 CCEA A-Level 地理规范所需的基本公式、模型和统计技术。内容涵盖自然地理计算（如河流流量、湿度和土壤含水量），以及人文地理指标（包括人口变化、抚养比、城市化和不平等衡量）。还包括斯皮尔曼等级相关和标准差等田野调查统计检验，以支持你的探究技能。
1. River Discharge and Flow Velocity | 河流流量与流速
River discharge is the volume of water passing through a given cross-section per unit time. It is fundamental for understanding flood hydrographs, channel efficiency, and catchment response to rainfall.
河流流量是单位时间内通过某一断面的水量。它是理解洪水过程线、河道效率和流域降雨响应的基础。
Q = A × V
Where: Q = discharge (cubic metres per second, m3 s-1), A = cross-sectional area (m2), V = mean velocity (metres per second, m s-1).
其中：Q 为流量（立方米每秒，m3 s-1），A 为横截面积（m2），V 为平均流速（米每秒，m s-1）。
In fieldwork, velocity is often measured using a float over a known distance: V = distance (m) / time (s).
在野外工作中，流速常通过浮标法测量已知距离得到：V = 距离 (m) / 时间 (s)。
2. Runoff and Water Balance | 径流与水平衡
The water balance equation summarises the inputs, outputs, and storage changes within a drainage basin over a given period.
水平衡方程总结了特定时段内流域的输入、输出和蓄水变化。
P = Q + E + ΔS
Where: P = precipitation, Q = runoff, E = evapotranspiration, ΔS = change in storage (all in mm or m3).
其中：P 为降水量，Q 为径流量，E 为蒸发蒸腾量，ΔS 为蓄水量变化（单位均为 mm 或 m3）。
The runoff coefficient indicates what fraction of rainfall becomes streamflow: C = Q / P. A higher coefficient suggests more rapid surface runoff and greater flood risk.
径流系数表示降雨转化为河川径流的比例：C = Q / P。系数越高，表明地表径流越快，洪水风险越大。
3. Relative Humidity | 相对湿度
Relative humidity (RH) measures how close the air is to saturation, affecting evapotranspiration, cloud formation, and human comfort.
相对湿度（RH）衡量空气接近饱和的程度，影响蒸发蒸腾、云的形成和人体舒适度。
RH (%) = (e / es) × 100
Where: e = actual vapour pressure (hPa), es = saturation vapour pressure (hPa) at the same temperature.
其中：e 为实际水汽压 (hPa)，es 为同温度下的饱和水汽压 (hPa)。
This relationship is used in climate diagrams, drought monitoring, and assessing potential evapotranspiration.
这一关系用于气候图表、干旱监测和估算潜在蒸散发。
4. Soil Moisture Content and Porosity | 土壤含水量与孔隙度
Soil moisture content and porosity are key physical properties influencing infiltration, throughflow, slope stability, and agriculture.
土壤含水量和孔隙度是影响下渗、壤中流、坡面稳定性和农业的关键物理属性。
Moisture content (%) = [(Mw – Md) / Md] × 100
Where: Mw = mass of wet soil, Md = mass of oven-dried soil.
其中：Mw 为湿土质量，Md 为烘干后干土质量。
Porosity (%) = (Vv / Vt) × 100
Where: Vv = volume of void spaces, Vt = total volume of the sample.
其中：Vv 为空隙体积，Vt 为样品总体积。
5. Population Change Metrics | 人口变化指标
Understanding population dynamics requires rates of birth, death, natural change, and net migration.
理解人口动态需要出生率、死亡率、自然变动和净迁移率。
CBR = (B / P) × 1000
CDR = (D / P) × 1000
CBR = crude birth rate per 1000, CDR = crude death rate per 1000, B = live births in a year, D = deaths in a year, P = mid-year total population.
CBR 为粗出生率（每千人），CDR 为粗死亡率（每千人），B 为年活产数，D 为年死亡数，P 为年中总人口。
Natural increase per 1000 = CBR – CDR
Population growth rate (%) = (CBR – CDR) / 10
When migration is included: Growth rate (%) = [(B – D + I – E) / P] × 100, where I = immigrants, E = emigrants.
当包含迁移时：增长率 (%) = [(B – D + I – E) / P] × 100，其中 I 为迁入人口，E 为迁出人口。
6. Dependency Ratio and Ageing Index | 抚养比与老龄化指数
These indicators show the burden on the working-age population and the pace of population ageing.
这些指标反映了劳动年龄人口的抚养负担和人口老龄化速度。
Dependency ratio (%) = [(P0-14 + P65+) / P15-64] × 100
P0-14 = population aged 0–14, P65+ = population aged 65 and over, P15-64 = working-age population.
P0-14 为 0–14 岁人口，P65+ 为 65
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